Method for operating microlithographic projection exposure apparatus, microlithographic mask and projection exposure apparatus

Abstract

The invention relates to a method for operating a microlithographic projection exposure apparatus (1), in which the following are provided in order to at least partially compensate for image shifts that result from, for example, the extent of dipole illumination (300) and ultimately result in an undesired loss of imaging contrast (M3D effect): field-dependent illumination, wherein different field regions of the object plane (6) are illuminated with different illumination settings, and a field-dependent image shift is generated during the imaging of the object plane onto the image plane (12). Here, the interaction between the field-dependent illumination and the field-dependent image offset may result in an overall reduction in the loss of imaging contrast. The field dependent illumination may be implemented, for example, by a MEMS facet mirror (20) in the illumination device (2), and the field dependent image offset may be implemented, for example, by horizontal and / or vertical mask distortion in combination with adaptive feed modification.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of German patent application DE 10 2023 127 297.7 filed on October 6, 2023. The content of this application is incorporated herein by reference. Technical Field

[0003] The invention relates to a method for operating a microlithography projection exposure apparatus, a microlithography mask and a microlithography projection exposure apparatus. Background Art

[0004] Microlithography is used to produce microstructured electronic components. The microlithography process is carried out in a so-called projection exposure apparatus, which has an illumination device and a projection lens. The image of the mask (=reticle) illuminated by the illumination device is projected by means of the projection lens onto a substrate (e.g. a silicon wafer) which has been coated with a photosensitive layer (photoresist) and is arranged in the image plane of the projection lens, in order to transfer the mask structure to the photosensitive coating of the substrate.

[0005] In projection lenses designed for the EUV range, for example at wavelengths of eg about 13 nm, about 11 nm, about 7 nm or about 4 nm, mirrors are used as optical components for the imaging process due to lack of availability of suitable light-transmitting refracting materials.

[0006] One problem that occurs in practice is that the three-dimensional mask effect (also called mask 3D effect or simply "M3D") causes wavefront tilt and image shift that depends on the illumination angle or illumination direction of the illumination on the mask. In large-area illumination (e.g. dipole illumination), this leads to image blurring and thus to reduced contrast of the image produced in the wafer plane, which can lead to serious problems with respect to the performance and quality of the lithography process.

[0007] Known methods for overcoming this problem include, inter alia, the use of new mask materials, new illumination modes and the known split dipole illumination, in which the exposure or scanning operation is divided into two exposure operations with different illumination polarities. However, the aforementioned known methods of split dipole illumination require an undesirable reduction in the throughput achieved in the lithography process and / or the generation of additional image errors, in particular overlay errors, and even with the remaining measures mentioned, this problem can only be solved to an unsatisfactory extent.

[0008] The following will refer to Figure 3 Explaining in more detail the problems associated with the offset in the case of dipole illumination in the prior art:

[0009] Figure 3 (corresponding to WO 2020 / 221556 A1 Figure 4) schematically shows an illumination pupil of an EUV projection exposure apparatus with dipole illumination, the two poles of which are only highlighted and hinted for clarity purposes. Due to the distance between the poles and the distance from the optical axis, as can be seen, an image shift of approximately -3 nm for one pole (in this example) and approximately +3 nm for the other pole occurs, that is to say an image shift of approximately 6 nm overall.

[0010] Figure 2 The resulting superimposed image in the image representation on the wafer plane is shown (likewise schematically). The incoherent superposition of the two monopole images (according to the continuous curve and the dashed curve, respectively) results in a point-shaped accumulation curve.

[0011] The cumulative curve shows that the intensity at the periphery does not return completely to zero, but only to a value of about 0.15, and the maximum value is also not 1.0 but slightly less than 0.9, with the result that the contrast ratio of 100% is reduced to about 75%, which, as already mentioned, can lead to serious performance and quality disadvantages.

[0012] In contrast, Figure 1 A situation with a reduced M3D effect according to the invention is shown, with the result that, as can be seen, the contrast ratio can be significantly improved to 90% in this example; this will be described in further detail below.

[0013] With regard to the prior art, reference is made purely by way of example to the already mentioned WO 2020 / 221556 A1 and DE 10 2014 217 611 A1. Summary of the invention

[0014] It is an object of the present invention to provide a method for operating a microlithography projection exposure device, a microlithography mask and a microlithography projection exposure device, by means of which the compensation of aberrations caused by mask structures to be imaged can be improved.

[0015] This object is achieved according to the features of the independent claims.

[0016] Advantageous developments of the invention are described in the dependent claims.

[0017] The method according to the invention is used to operate a microlithography projection exposure apparatus having an illumination device and a projection lens, wherein the illumination device illuminates a mask located in an object plane of the projection lens, and the projection lens images structures on the mask onto a photosensitive layer located in an image plane of the projection lens, wherein during a scanning operation, the corresponding illuminated areas of the mask are changed.

[0018] The lighting device can in particular have a spatially extended radiation field having two or more illumination poles which are spaced apart horizontally (i.e. in the x-direction) and / or vertically (i.e. in the y-direction), which, as described above, leads to an image shift on the photosensitive layer and therefore to an undesirable loss of imaging contrast due to the M3D effect.

[0019] The method according to the invention is characterized in that

[0020] - the illumination of the mask takes place as field-dependent illumination, in which different field regions of the object plane are illuminated with different illumination settings, and

[0021] During the imaging of the object plane onto the image plane, a field-dependent image shift is generated, wherein different field regions of the object plane are converted into different image shifts.

[0022] Here, illumination settings are understood to mean the intensity distribution in a pupil plane of the illumination device.

[0023] According to one embodiment, the interaction between field-dependent illumination and field-dependent image shift results in an increase in imaging contrast during imaging onto an image plane compared to imaging without the field-dependent image shift.

[0024] In other words, due to field-dependent illumination, the illumination distribution is modified in a field-dependent manner so that when a field-dependent image shift occurs, the modification can be achieved in a manner that compensates for the interference shift, so that the resulting image shift can be reduced overall and the imaging contrast can therefore be increased.

[0025] According to an embodiment, the mask is illuminated via an elongated scanning slit, in particular in the shape of a circle segment, wherein the scanning direction extends transversely to the scanning slit, and wherein during the scanning operation a plurality of field regions of the object plane are illuminated in each case with different illumination settings. Here, in particular, at least two field regions of the object plane can overlap with one another.

[0026] According to an embodiment, a field-dependent image shift is generated during imaging onto the image plane, depending on the lateral direction position of the radiation incident on the scanning slit.

[0027] In other words, the variation in the degree of freedom transverse to the scanning slit, ie in the y direction (scanning direction), is used to image the individual poles more or less individually in this transverse direction with field-dependent illumination in order to thereby generate the desired compensating shift via a field-dependent image shift.

[0028] According to one embodiment, field-dependent illumination of the mask takes place via a faceted mirror arrangement or a mirror array arrangement with a microelectromechanical system (MEMS), wherein radiation from a first illumination pole results in illumination predominantly in the lower region of the scanning slits and radiation from a second illumination pole results in illumination predominantly in the upper region of the scanning slits.

[0029] In a refinement, the offset compensation according to the invention can be performed particularly effectively if a separate dark field is provided between the illumination in the upper region of the scanning slit and the illumination in the lower region of the scanning slit.

[0030] In an embodiment of the invention, a field-dependent image shift can be generated via a distortion profile integrated into the mask structure.

[0031] In particular, for this purpose, the horizontal mask structure and / or the vertical mask structure can each have a specified distortion profile. In this respect, the mask feed and / or the feed of the photosensitive layer is correspondingly modified during the scanning operation compared to the nominal mask feed to compensate for the distortion profile.

[0032] Here, a difference arises depending on whether the illumination poles spaced apart in each case during illumination of the mask are arranged vertically or horizontally in the main direction of the scanning slit:

[0033] - in order to reduce the image shift in the case of horizontally spaced illumination poles (for imaging preferably vertically oriented structures), the mask structure should preferably be distorted in the horizontal direction, wherein this horizontal distortion can be compensated by an additional shifting shift of the mask and / or the photosensitive layer in the horizontal direction;

[0034] - In order to reduce image shifts in the case of vertically spaced illumination poles (for imaging predominantly horizontally oriented structures), the mask structure should preferably be distorted in the vertical direction, wherein this vertical distortion can be compensated by a feed speed between mask and photosensitive layer which deviates from the nominal feed speed.

[0035] A diagonal arrangement or orientation of the illumination pole relative to the main direction of the scanning slit is likewise conceivable and would imply a combination of the two aforementioned measures.

[0036] The proposed mask distortion tends to result in a degradation of the imaging quality of the dipole single images. However, taking into account the achievable offset compensation according to the invention, this effect fades into the background, in other words, there is an optimal compromise as will be explained in further detail below.

[0037] Even though the invention as part of the present disclosure is described primarily using dipole illumination devices, the application of the invention should not be restricted to dipole illumination devices but can also (possibly with appropriate modifications) be used for offset compensation in other illumination sources which are not approximated in the form of a single point (e.g. approximated line illumination sources or complex illumination pupils optimized by SMO (= “Source Mask Optimization”)) and possibly also in the case of n-pole illumination with n>2 (e.g. quadrupole illumination).

[0038] For possible illumination settings, reference is made by way of example to the publication by L. Wischmeier et al.: “High-NAEUV Lithography Optics Becomes Reality”, Proc. SPIE 11323, Extreme Ultraviolet (EUV) Lithography XI, 1132308 (March 23, 2020); doi:10.1117 / 12.2543308, see also Figure 3 b and 3c.

[0039] In a preferred embodiment of the invention, the above-mentioned distortion in a ring-segment-shaped scanning slit extending in the horizontal direction and in which the field-dependent illumination distribution varies in the lateral direction can be realized in a first approximation according to one or more of the following transformation formulas:

[0040] - The distortion of the vertical mask structure according to

[0041] (x,y)->(x+dfx*(y-rfs(x)),y),

[0042] and / or

[0043] - Distortion of the horizontal mask structure according to the following formula

[0044] (x,y)->(x,y+dfy*(y-rfs(x))),

[0045] in:

[0046] rfs(x) describes the profile of the y-component of a specified distortion zero line for the scanning slit depending on the x-position, and

[0047] dfx and dfy represent the specified vertical or horizontal distortion factors, where the two factors can also be the same.

[0048] In further embodiments, a field-dependent image shift may (alternatively or possibly additionally) be achieved by manipulations performed during a scanning operation within the projection lens.

[0049] Furthermore, as part of the invention a microlithography mask is proposed, which mask is designed for use in the previously described method, i.e., the mask is designed specifically using a target distortion for producing a field-dependent image shift or at least as an essential component thereof (after all, the entire field-dependent image shift typically additionally includes a compensating adaptation in the mask / wafer feeding).

[0050] Furthermore, as part of the invention a projection exposure apparatus is proposed which is designed to carry out the method described above.

[0051] Further developments of the invention are evident from the description and the dependent claims.

[0052] The invention is explained in more detail below based on the exemplary embodiments shown in the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In the attached picture:

[0054] Figure 1 and Figure 2 A spatially dependent intensity plot illustrating the imaging quality on a wafer exposed to dipole illumination is shown, where Figure 1 shows an intensity distribution with offset compensation according to the invention, and Figure 2 The distribution without this offset compensation is shown for comparison purposes;

[0055] Figure 3 A schematic diagram illustrating the formation of an imaging shift in the case of symmetric dipole illumination is shown;

[0056] Figure 4 A schematic diagram showing the separation of dipole illumination into an upper field and a lower field having a horizontal dipole orientation is shown;

[0057] Figure 5 A schematic diagram showing horizontal mask distortion for distortion compensation with horizontal dipole orientation is shown;

[0058] Figure 6 A schematic diagram showing the intensity distribution in the scanning direction caused by horizontal mask distortion;

[0059] Figure 7a , 7b shows a schematic diagram for illustrating the effect of horizontal mask distortion in a write mask structure;

[0060] Figure 8 A schematic diagram showing the division of dipole illumination into an upper field and a lower field with vertical dipole orientation (for imaging primarily horizontal structures) is shown;

[0061] Fig. 9 Schematic diagram showing horizontal mask distortion for distortion compensation with vertical dipole orientation;

[0062] Fig.10 A schematic diagram showing the intensity distribution in the scanning direction caused by vertical mask distortion;

[0063] Fig.11a , 11b A schematic diagram for illustrating vertical mask distortion in a write mask structure is shown;

[0064] Fig.12 shows a graph illustrating the achievable contrast ratio as a function of the distortion factor;

[0065] Fig.13 Schematic diagram showing a MEMS faceted mirror arrangement for implementing field dependent illumination;

[0066] Fig.14 shows a schematic illustration of an embodiment with a narrower field division, with a separate dark field located therebetween;

[0067] Fig.15 Shown by Fig.14 The intensity distribution produced by the intensity distribution of

[0068] Fig.16 and 17 shows the intensity distribution with no offset ( Fig.16 ) with narrower field division and distortion factor of 4nm / mm ( Fig.17 ) is a schematic diagram of the intensity distribution in the scanning direction; and

[0069] Fig.18 Shown is a schematic diagram of a projection exposure apparatus designed for operation in the EUV range. DETAILED DESCRIPTION

[0070] The embodiments described below have in common that, during operation of the microlithography projection exposure device, field-dependent illumination during a scanning operation is combined with an image shift produced in a targeted manner to compensate for three-dimensional mask effects and associated undesirable contrast reductions, wherein this image shift is implemented in different ways depending on the embodiment.

[0071] Figure 1-3 A schematic diagram is shown for illustrating the concept according to the invention, which has already been explained in more detail in the introduction.

[0072] like Figure 3 As shown, the imaging offset between the two dipole illumination sources 301, 302 (indicated as a whole by 300) is about 6 nm in this example, according to Figure 2, in the incoherent superposition imaging between the left pole 200 and the right pole 201 on the wafer, the sum 202 reaches a contrast ratio reduced to about 75%, with corresponding disadvantages in the performance and quality of the entire lithography process.

[0073] By using the offset compensation according to the present invention, according to Figure 1 An improved contrast ratio of approximately 93% in this example can be achieved by reducing the offset between the left pole 100 and the right pole 101 (see Figure 1 The cumulative intensity in 102).

[0074] However, the offset compensation measures described in more detail further below tend to be detrimental to the contrast ratio of the imaging of the individual poles, as can be seen from a comparison between the curves 100, 101 and 200, 201; the individual curves 100, 101 are slightly flatter than the curves 200, 201, i.e., Figure 2 In comparison, the individual contrast ratios are reduced to approximately 95%, which, however, in this example, means a significant contrast improvement of the integrated intensity 102 due to the reduced offset.

[0075] Realization of field-related lighting

[0076] To achieve the desired offset compensation, it is first necessary to generate a field-dependent illumination distribution, wherein different field regions of the object plane are illuminated with different illumination settings, so that the radiation from the individual illumination poles is converted into different illumination distribution patterns in a field-dependent or pole-dependent manner.

[0077] like Fig.13 As shown, this can be achieved by a MEMS (micro-electromechanical system) arrangement with a large number of individually actuatable mirrors within the lighting device, wherein Fig.13 Different orientations of the mirrors (not shown to scale) in the right part of are shown in different grey levels.

[0078] This MEMS facet mirror can be used as a field mirror 20 in a microlithography projection exposure apparatus in an illumination device, which will be referred to below. Fig.18 Explain in more detail.

[0079] The use of variably actuated mirrors in the context of the present invention has the additional advantage that the offset compensation can be combined with components, which will be explained further below, which are changed or optimized or optionally even deactivated, i.e. the arrangement according to the invention can be operated without "conventionally" significant physical modifications and with offset compensation.

[0080] Fig.13The tilt pattern of the mirror facets shown in is essentially static during operation of the device and produces a very correlated separation intensity distribution on the mask, as described further below, preferably transverse to the scanning slit range (ie, in the y-direction).

[0081] In this way, the illumination is divided into two areas, provided that the upper part of the scanning slit is illuminated only (or at least predominantly) with one illumination pole of the dipole setting, while the lower part of the scanning slit is illuminated only or predominantly with the corresponding other illumination pole of the dipole setting; however, a peripheral overlap of the areas is in principle possible.

[0082] Alternatively, this effect can also be achieved without the use of MEMS by a "fixed" facet mirror which is split into two parts, wherein the individual parts (not shown) have individually adjustable tilts.

[0083] Another alternative possibility for achieving a field-dependent illumination distribution is described in WO 2016 / 034424 A1, which is intended to be incorporated herein by reference, since the partial field grouping described therein (which can be obtained by means of a two MEMS mirror arrangement) is used by means of a “jigsaw-type” control of the mirror facets in a targeted manner relative to the polar-dependent intensity distribution desired here.

[0084] Implementation of Field-Dependent Image Migration

[0085] Starting from a field-dependent illumination, a field-dependent image shift is generated according to the invention, which leads to at least partial compensation of an unwanted image shift.

[0086] In this regard, a particularly suitable measure is a tilting deformation of the mask or reticle, which will be referred to as Figures 4 to 11b This is explained in conjunction with the corresponding adjustment of the feed speed.

[0087] Here, in a vertical mask structure (cf. Figures 4 to 7b ) and a horizontal mask structure with a substantially vertical dipole orientation (see Figures 8 to 11b ) are distinguished between.

[0088] In the case of a substantially horizontal dipole (or illumination source with comparable geometry), e.g. Figure 4 As indicated in FIG. 4 , the offset between the upper field 400 (illuminated by the right dipole, see 402 ) and the lower field 401 (illuminated by the left dipole, see 403 ) is compensated by Figure 5 The vertically tilted distortion mask structure described in is implemented in combination with a compensatory x-shift of the wafer.

[0089] In principle, preferably horizontally oriented dipoles are used to image vertical structures (i.e. vertically oriented lines). The shift of these structures due to the M3D effect extends in the horizontal orientation. Therefore, the correction (i.e. additional mask distortion and subsequent movement of the stage) must also take place in the horizontal direction.

[0090] exist Figure 5 In the figure, the distorted structure (not drawn to scale, the distortion is a factor of 10 5 The distorted "straight" structure is shown in dashed lines for comparison purposes (as a reference point).

[0091] It can be seen that the distortion is zero in each case along the center line of the curved scanning slit and increases further upwards or downwards with corresponding opposite signs in particular according to a linear relationship, which has already been mentioned further above and is valid in a first approximation.

[0092] (x,y)->(x+dfx*(y-rfs(x)),y), where

[0093] rfs(x) describes the profile of the y-component of a specified distortion zero line for the scanning slit depending on the x-position, and

[0094] dfx represents the specified vertical distortion factor; typical values ​​of dfx range from about 1-10 nm / mm.

[0095] In this way, one can then implement Figure 6 Intensity distribution shown, where a substantially constant cumulative intensity can be achieved over the central area (dashed line).

[0096] exist Figures 8 to 11b In the variation shown, vertical mask distortion structures (i.e., those acting in the y-direction) are useful with substantially vertically oriented dipoles for imaging horizontal structures, such as Fig. 9 as well as Fig.11a and Fig.11b shown.

[0097] Here, no distortion is provided along the center line either, but in the y direction, in each case a distortion with a different sign is provided upwards and downwards in the y direction, resulting in a compensating offset of the upper and lower regions 801, 802 illuminated by the corresponding poles (802, 803), resulting in a Fig.10 , resulting in the same situation as above (see Figure 6 ) with comparable intensity distribution.

[0098] In this case, the distortion can be described mathematically in a first approximation as follows:

[0099] The distortion of the horizontal mask structure is given by

[0100] (x,y)->(x,y+dfy*(y-rfs(x))), where:

[0101] rfs(x) is defined as above, and

[0102] dfy represents the specified horizontal distortion factor (also commonly described as sf in an orientation-independent manner).

[0103] To compensate for vertical mask distortions, the mask and wafer stage must additionally be moved with a slightly different feed speed (eg, with a feed speed that deviates from the nominal feed speed) according to a specified distortion factor.

[0104] Furthermore, in case of vertical distortions, a specific adaptation of the intensity distribution between the upper field region 800 and the lower field region 801 may be required during fine optimization in order to compensate for the different angles of incidence between the upper and lower pole illumination.

[0105] Even though the implementation of a field-dependent image shift is described above with reference to mask distortions and corresponding adjustments in mask feed / wafer feed, the invention is explicitly not limited to this implementation. Compensating shifts can also be implemented, for example, by additional optical elements in the beam path.

[0106] Optimization of contrast ratio

[0107] The above-mentioned distortions of the mask itself also cause imaging errors, which lead to a reduction in the contrast ratio. As the distortion factors are increased with the aim of fully compensating the image shift, the individual contrast ratios are therefore reduced at the same time, which is why this is ultimately an optimization problem, according to Fig.12 As shown in the diagram in FIG. 1 , the optimization problem has a maximum value at a distortion factor of about 4 nm / mm in an exemplary embodiment, which does not imply full offset compensation, see the discussion in the introduction section. Figure 1 Intensity map in , which is based on a corresponding shift of approximately sf = 4 nm / mm.

[0108] In order to achieve further improvement in contrast ratio, such as Fig.14 The two illuminated fields can be more strictly depicted relative to each other, as schematically shown in FIG. 1 , based on narrow bands 1400, 1401 separated by a dark field 1402, with the result that, according to Figures 15 to 17 , obtaining an almost optimal contrast ratio of approximately 99%, see the case with no offset (sf=0) Fig.16 Compared with the distortion factor sf=4nm / mm Fig.17 .

[0109] However, such a narrow illumination profile leads to a reduction in the effective etendue of the system, which can result in undesired losses of light sources that are incoherent here.

[0110] Fig.18 A possible setup of a microlithography projection exposure tool designed for operation in the EUV range is schematically shown in a meridional section.

[0111] according to Fig.18 , the projection exposure apparatus 1 comprises an illumination device 2 and a projection lens 10. An embodiment of the illumination device 2 of the projection exposure apparatus 1 has, in addition to a light or radiation source 3, an illumination optical unit 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a module separate from the rest of the illumination device. In this case, the illumination device does not comprise the light source 3.

[0112] Here, a mask 7 arranged in the object field 5 is exposed. The mask 7 is held by a mask holder 8. The mask holder 8 can be displaced, in particular in the scanning direction, via a mask displacement drive 9. For explanation purposes, Fig.18 A Cartesian xyz coordinate system is depicted in FIG. The x direction extends perpendicular to the plane of the drawing. The y direction extends horizontally and the z direction extends vertically. The scanning direction is Fig.18 The z direction extends perpendicular to the object plane 6. In an embodiment of the present invention, the mask holder 8 can also be displaced in the x direction. In addition, in an embodiment of the present invention, a controller for changing the scanning speed is also provided.

[0113] The projection lens 10 serves to image the object field 5 into an image field 11 in an image plane 12. The structures on the reticle 7 are imaged onto a photosensitive layer 24 of a wafer 13, which is arranged in the region of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced, in particular in the y direction, by a wafer displacement drive 15. The displacement of the reticle 7 via the reticle displacement drive 9 on the one hand and the displacement of the wafer 13 via the wafer displacement drive 15 on the other hand can be performed synchronously with one another.

[0114] The radiation source 3 is an EUV radiation source. The radiation source 3 in particular emits EUV radiation, which is also referred to as used radiation or illumination radiation in the following text. In particular, the used radiation has a wavelength in the range between 5 nm and 30 nm. The radiation source 3 can be, for example, a plasma source, a synchrotron-based radiation source or a free electron laser (FEL). The illumination radiation 16 emitted from the radiation source 3 is focused by a collector 17 and propagates into the illumination optical unit 4 through an intermediate focus in an intermediate focal plane 18. The illumination optical unit 4 comprises a deflection mirror 19 and a first facet mirror 20 (with a schematically indicated facet 21) and a second facet mirror 22 (with a schematically indicated facet 23) arranged downstream thereof in the beam path. The illustrated illumination optical unit 4 is only an example, wherein, depending on the embodiment, for example the deflection mirror 19 can also be arranged at a different position or even not exist at all.

[0115] The first facet mirror 20 is also called a field facet mirror and the second facet mirror 2 is also called a pupil facet mirror.

[0116] In the context of the present invention, provision may in particular be made for the field facet mirror 20 to be designed as a MEMS mirror having individually tilt-adjustable facets, with which a pole-dependent illumination distribution can then be set.

[0117] The projection lens 10 comprises a plurality of mirrors Mi (i=1, 2, . . . ), which are numbered according to their arrangement in the beam path of the projection exposure apparatus 1. Fig.18 In the example shown, the projection lens 10 comprises six mirrors M1 to M6. Alternatives with four, five, seven, eight, ten, twelve or a different number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have a through-opening for the illumination radiation 16. The projection lens 10 is a doubly shaded optical unit. Individually shaded optical units, in which only one mirror has a through-opening for the illumination radiation, or optical units that are not shaded at all are likewise possible. The projection lens 10 has an image-side numerical aperture that is greater than 0.5 and can also be greater than 0.6 and can be, for example, up to 0.85.

[0118] With the offset compensation possibilities presented according to the invention, the mask stack is subject to lower restrictions in this respect (with respect to absorbing materials and thickness) and can therefore be further optimized, for example with respect to imaging quality (eg contrast and reflectivity).

[0119] Horizontal and vertical offset structures can also be combined in principle.

[0120] Compensation of higher-order aberrations is also conceivable, but this seems to be better achieved by wavefront modification in the projection optics unit.

[0121] Furthermore, it is conceivable to divide the lighting into more than two areas in order to achieve a finer control over the M3D effect.

[0122] Although the present invention has been described based on specific embodiments, many variations and alternative embodiments will be apparent to those skilled in the art, such as by combining and / or exchanging the features of the various embodiments. Therefore, it is self-evident to those skilled in the art that these variations and alternative embodiments are also included in the present invention, and the scope of the present invention is limited only to the meaning of the attached patent claims and their equivalents.

Claims

1. A method for operating a microlithography projection exposure apparatus (1), the microlithography projection exposure apparatus (1) having an illumination device (2) and a projection lens (10), wherein the illumination device (2) illuminates a mask (7) located in an object plane (6) of the projection lens (10), and the projection lens (10) images structures on the mask (7) onto a photosensitive layer (24) located in an image plane (12) of the projection lens (10), wherein individual illuminated areas of the mask are changed during a scanning operation, characterized in that • the illumination of the mask (7) takes place as field-dependent illumination, wherein different field regions of the object plane (6) are illuminated with different illumination settings, and • During the imaging of the object plane onto the image plane (12), a field-dependent image shift is generated, wherein different field regions of the object plane (6) are converted into different image shifts.

2. The method according to claim 1, characterized in that The interaction between the field-dependent illumination and the field-dependent image shift leads to an increase in imaging contrast during imaging onto the image plane (12) compared to imaging without a field-dependent image shift.

3. The method according to claim 1 or 2, wherein: The mask (7) is illuminated via an elongated scanning slit, which is in particular in the shape of a circle segment, wherein the scanning direction extends transversely to the scanning slit, and wherein during the scanning operation a plurality of field regions of the object plane (6) are illuminated in each case with different illumination settings.

4. The method according to claim 3, characterized in that At least two field regions of the object plane (6) overlap with each other.

5. The method according to claim 3 or 4, characterized in that: The field-dependent image shift is generated during imaging onto the image plane (12) as a function of the transverse position of the radiation incident on the scanning slit.

6. The method according to any one of claims 3 to 5, characterized in that Field-dependent illumination of the mask (7) occurs via a faceted mirror arrangement or a mirror array arrangement with a microelectromechanical system (MEMS), wherein radiation from a first illumination pole (301) results in illumination predominantly in the lower region of the scanning slit and radiation from a second illumination pole (302) results in illumination predominantly in the upper region of the scanning slit.

7. The method according to claim 6, characterized in that A split dark field is provided between illumination in an upper region of the scanning slit and illumination in a lower region of the scanning slit (1402).

8. The method according to any one of the preceding claims, characterized in that The field-dependent image shift is achieved by horizontally extending mask structures of the mask (7) and / or vertically extending mask structures of the mask (7), the horizontally extending mask structures of the mask (7) and / or the vertically extending mask structures of the mask (7) each having a specified distortion profile, wherein the mask feed and / or the feed of the photosensitive layer (24) occurring during the scanning operation is modified relative to a nominal mask feed in order to compensate for the distortion profile.

9. The method according to claim 8, characterized in that - during illumination of the mask (7) with horizontally spaced illumination electrodes, the mask structure of the mask (7) is distorted in the horizontal direction, wherein the horizontal distortion is compensated by an additional shifting offset of the mask (7) and the photosensitive layer (24) in the horizontal direction; and / or - During illumination of the mask (7) with vertically spaced illumination electrodes, the mask structure of the mask (7) is distorted in the vertical direction, wherein the vertical deformation is compensated by a feed speed between the mask (7) and the photosensitive layer (24) which deviates from a nominal feed speed.

10. The method according to claim 9, characterized in that The distortion of the mask structure in a ring-segment-shaped scanning slit, which extends in the horizontal direction and in which the field-dependent illumination distribution varies in the lateral direction, is achieved at least approximately according to one or more of the following transformation formulas: - distortion of the vertical mask structure according to (x,y) -> (x+dfx*(y-rfs(x)),y), and / or - distortion of the horizontal mask structure according to (x,y) -> (x,y + dfy * (y - rfs(x))), in: rfs(x) describes the profile of the y-component of a given distortion zero line of the scanning slit as a function of the x-position, and dfx and dfy represent the specified vertical or horizontal distortion factors, where the two factors can also be the same.

11. The method according to any one of claims 1 to 5, characterized in that The field-dependent image shift is achieved by a manipulation performed during a scanning operation within the projection lens (10).

12. A microlithography mask (7), characterized in that: The microlithography mask is designed for use in a method according to any one of claims 1 to 11.

13. A microlithography projection exposure apparatus (1) designed to carry out the method according to any one of claims 1 to 11.

Images