Illumination optical unit, and method for measuring the dependence of an intensity of illumination light, incident on an object field, on at least one detection object field coordinate using such an illumination optical unit

Abstract

The invention relates to an illumination optical unit (11) having two facet mirrors (6, 7) for the reflective guiding of illumination light (2) of an EUV light source (2). The second facet mirror (7) has second individual mirrors (34), which form second facets (25) which image, via sub-bundles (30) of the illumination light (3), individual mirror groups (26) of the first facet mirror (6) which form first facets, at least in partial fields of an object field (8). An intensity sensor device (31) is used to measure the dependence of an intensity of the illumination light (3), which is incident on the object field (8), on at least one detection object field coordinate (x). Said intensity sensor device has individual sensor mirrors (21s) of the first facet mirror (6), which are allocated to a plurality of different object field positions (xi) along the detection object field coordinate (x). The individual sensor mirrors (21s) are designed to reflectively guide the illumination light (3) to intensity sensors (32i) of the intensity sensor device (31). This results in an illumination optical unit which makes it possible to measure a corresponding intensity coordinate dependence precisely and in parallel to a usage mode of the illumination optical unit.

Description

[0001] Illumination optics and method for measuring a dependence of an intensity of illumination light incident on an object field on at least one detection object field coordinate using such an illumination optics

[0002] This patent application claims priority from German patent application DE 10 2023 209 697.8, the contents of which are incorporated herein by reference.

[0003] The invention relates to an illumination optics system with two facet mirrors. Furthermore, the invention relates to a method for measuring the dependence of the intensity of illumination light incident on an object field on at least one detection object field coordinate using such an illumination optics system.

[0004] An illumination optic of the type mentioned above is known from DE 10 2015 208 512 Al.

[0005] It is an object of the present invention to further develop an illumination optics of the type mentioned at the outset and a measurement method therefor in such a way that a measurement of a dependence of an intensity of illumination light incident on the object field on at least one detection object field coordinate is enabled precisely and / or parallel to a useful operation of the illumination optics.

[0006] This object is achieved according to the invention by an illumination optics with the features specified in claim 1 and by a measurement method with the features specified in claim 6. According to the invention, it was recognized that in illumination optics with two facet mirrors, in particular in illumination optics in which at least one of the two facet mirrors is designed as a MEMS mirror with a very large number of individual mirrors, due to the great flexibility in the assignment of the individual mirrors of the two facet mirrors for guiding the illumination light within the illumination optics, it regularly happens that certain individual mirrors of the first facet mirror are not used for projection exposure within the illumination optics.Illumination light incident on these individual mirrors of the first facet mirror can be used in the illumination optics according to the invention to measure the dependence of the intensity of illumination light incident on an object field on at least one detection object field coordinate. This utilizes the knowledge that the individual mirrors of the first facet mirror not used for object field illumination, due to their arrangement on the first facet mirror, allow a conclusion to be drawn about which object field coordinates are illuminated along the detection object field coordinate to be measured by individual mirrors used for projection exposure, which are adjacent to these individual sensor mirrors.This insight, which allows the assignment of the respective individual sensor mirrors to the object field coordinate to be detected, and the realization that a far-field illumination intensity dependence across the first facet mirror regularly changes only slightly when viewed across the dimensions of an individual mirror, leads to the possibility of using the intensity sensor device of the illumination optics to precisely measure the dependence of the illumination intensity on the detection object field coordinate, and also to the possibility of performing the measurement parallel to the operational operation of the illumination optics. By assigning the first facets to the second facets, an illumination setting, i.e., an illumination angle distribution of the illumination of the object field, can be specified.The illumination intensity distribution over the object field coordinate to be detected may depend on the selected illumination setting and it may therefore be necessary to monitor this illumination intensity distribution depending on the setting and to correct it if necessary.

[0007] Even short-term changes in intensity can be detected and, if necessary, corrected as part of ongoing monitoring with the intensity sensor device during operation.

[0008] The illumination optics can be designed with a field facet mirror and a pupil facet mirror, with the second facet mirror being arranged in the region of a pupil plane of the illumination optics. Alternatively, the illumination optics can also be designed in the manner of a specular reflector, with the second facet mirror being arranged at a distance from an illumination pupil plane.

[0009] The intensity sensor device can be used, in particular, as a field-resolving UNICOM sensor. A corresponding device for influencing the uniformity of illumination intensity across the field height can then be controlled via the intensity sensor device. Such an influencing device, also known as UNICOM, is known from EP 0 952 491 A2.

[0010] The intensity sensors of the intensity sensor device can correspond to the second facets in terms of their edge shape and / or area. Light loss due to overexposure of the second facets, i.e., to the extent that illumination light is lost beyond the second facets, is then similar to light loss due to overexposure of the intensity sensors. In particular, a design can be achieved in which the sensor signal of the intensity sensors remains proportional to the intensity of the illumination light arriving in the object field even if light loss of the object field illumination varies over time, e.g., due to drifts of the EUV light source.

[0011] If the illumination optics are designed such that the design of the second facets, and in particular the number and arrangement of the second individual mirrors forming the second facets, is variable depending on the illumination configuration, the associated intensity sensors can also have a variable size or a variable edge shape, adapted to this size variability. Such a variable size or edge shape of the intensity sensors can be achieved by specifying intensity sensors of different sizes. Alternatively or additionally, a variability in the size orthe edge shape of the intensity sensors can be achieved by apertures assigned to the intensity sensors in the illumination light beam path in front of the intensity sensors and / or by a pixel design of the intensity sensors, whereby depending on the size and shape of the second facets, such pixelated intensity sensors are only read out at the sensor pixels whose arrangement corresponds to the size or shape of the second facets.

[0012] Depending on the requirements profile, the number of intensity sensors according to claim 2 enables sufficient spatial resolution for the detection object field coordinate to be measured. When measuring a detection object field coordinate, the number of intensity sensors can be in the range between 4 and 100, in the range between 5 and 50, for example, in the range of 10 or in the range of 25. If two field dimensions are to be measured, for example, if the far field in which the first facet mirror is arranged is to be measured using the intensity sensor device, the number of intensity sensors can also be greater than 100 and can be in the range between 100 and 1000.

[0013] An arrangement of intensity sensors according to claim 3 utilizes the fact that the illumination light in the region of the second individual mirrors is usually present in a facet-channel-bundled form, since in a typical application, an at least approximate image of the light source into an arrangement plane of the second facet mirror occurs there. The arrangement of the intensity sensors adjacent to the second individual mirrors of the second facet mirror then makes it possible to arrange the intensity sensors compactly next to one another.

[0014] A sensor line according to claim 4 is particularly compact.

[0015] An arrangement of the individual sensor mirrors according to claim 5 enables a 2D far-field measurement, wherein the measuring positions of the individual sensor mirrors serve as measuring support points, from which an extrapolation can then be carried out to determine the entire 2D far-field.

[0016] The advantages of a method according to claim 6 correspond to those already explained above in connection with the illumination optics. This results in a particularly precise measurement of the dependence of the intensity of the illumination light on the detection object field coordinate, which can in particular take place parallel to a useful operation of the illumination optics. In preparation for the evaluation step of the measurement method, the intensity sensors can be calibrated, for example, using an illumination arrangement with constant illumination intensity across the detection object field coordinate. The evaluation step can be followed by a correction step in which an individual mirror assignment or a facet assignment is changed such that an actual value of an illumination intensity distribution across the detection object field coordinate approaches a target value.The resulting correction can in particular be carried out in such a way that an illumination angle distribution of an illumination of the object field by the illumination optics remains unchanged due to the correction.

[0017] The advantages of the method according to claim 7 correspond to those of the illumination optics according to claim 5.

[0018] The advantages of an illumination system according to claim 8, an optical system according to claim 9, a projection exposure system according to claim 10, a manufacturing method according to claim 11, and a micro- or nanostructured component according to claim 12 correspond to those already explained above with reference to the illumination optics according to the invention and the measurement method according to the invention. Due to the precisely measured and, if necessary, corrected illumination intensity distribution across the detection object field coordinate, the possibility of particularly precise and high-resolution component production arises. In the manufacturing method according to claim 11, the measurement method discussed above can be used in particular to specify an optimized illumination setting.

[0019] In particular, a semiconductor component in the form of a microchip, in particular a memory chip, can be produced.

[0020] Embodiments of the invention are explained in more detail below with reference to the drawings, in which:

[0021] Fig. 1 shows a highly schematic meridional section of a projection exposure system for EUV microlithography with a light source, an illumination optics and a projection optics, with an insert showing a plan view of an object field of the projection exposure system;

[0022] Fig. 2 schematically and also in meridional section a beam path of selected individual beams of illumination light within the illumination optics according to Fig. 1, starting from an intermediate focus up to a reticle or object arranged in the object plane of the projection optics in the region of the illumination or object field;

[0023] Fig. 3 is a plan view of a section of a first facet mirror of the illumination optics of the projection exposure system, wherein an individual mirror group of the first facet mirror, which forms a first facet, is highlighted, which is imaged into the object field by means of a partial beam of the illumination light via individual mirrors of a second facet mirror of the illumination optics, which form a second facet;

[0024] Fig. 4 shows, in a representation similar to Fig. 3, a section of a further embodiment of the first facet mirror, again with a highlighted individual mirror group which is imaged into the object field as a first facet via an associated second facet of the second facet mirror;

[0025] Fig. 5 shows, in a representation similar to Figs. 3 and 4, a plan view of the first facet mirror with an arrangement of individual mirrors corresponding to Fig. 4, wherein an occupancy of the first facet mirror with first facets, each formed from individual mirror groups, is illustrated, which are imaged in the object field in an overlapping manner, wherein between these individual mirror groups, individual sensor mirrors of an intensity sensor device for measuring a dependence of an intensity of the illumination light incident on the object field on a detection object field coordinate are additionally highlighted;

[0026] Fig. 6 shows schematically and in perspective an embodiment of the illumination optics of the projection exposure apparatus with the first facet mirror and the second facet mirror, wherein an illumination light beam path between a light source and an intensity sensor of an intensity sensor sensor row of the intensity sensor device, guided via one of the individual sensor mirrors of the first facet mirror, is illustrated;

[0027] Fig. 7 is a diagram showing a correlation NG (ordinate) of the field height coordinates x within a respective column of a column-wise assignment of the individual mirror groups of a variant of the first facet mirror to field heights x of the object field of the first facet mirror (abscissa), when setting an illumination setting “y-dipole”, whereby the assignment of the individual mirrors to the field heights x leads to a total of eight individual mirror columns (j=l, . . .8);

[0028] Fig. 8 shows an example of a distribution of the individual sensor mirrors on a variant of the first facet mirror with a much larger number of individual mirrors compared to Fig. 5, again in a top view;

[0029] Fig. 9 shows a diagram showing a field height dependence of a target illumination intensity ISOLL (dashed line) over the object field and an as yet uncorrected actual illumination light intensity IIST (solid line);

[0030] Fig. 10 in a representation similar to Fig. 9 intensity measured values ​​of the intensity sensors over the sensor line according to Fig. 6, where correction measured values ​​I K (dashed) for the case of the target illumination intensity according to Fig. 9 and actual measured values ​​I M(solid) for the case of the still uncorrected illumination intensity distribution according to Fig. 9; and Fig. 11 a comparison of relative changes in the field height dependencies on the one hand for the illumination with the actual illumination intensity according to Fig. 9 as relative intensity deviation IisT (dashed) and on the other hand as relative measured value deviation IIST M between the two measurement curves according to Fig. 10 (solid), to illustrate a measurement quality of the intensity sensor device, which can be used for a subsequent correction.

[0031] A projection exposure system 1 for microlithography, shown in Figure 1 in a highly schematic and meridional section, has a light source 2 for illumination light 3. The light source 2 is an EUV light source that generates light in a wavelength range between 5 nm and 30 nm. This can be an LPP (laser-produced plasma) light source, a DPP (discharge-produced plasma) light source, or a synchrotron radiation-based light source, for example, a free-electron laser (FEL).

[0032] A transmission optics system 4 is used to guide the illumination light 3, emanating from the light source 2. This system has a collector 5, shown in Fig. 1 only with regard to its reflective effect, and a transmission facet mirror 6, which will be described in more detail below and is also referred to as a first facet mirror or a field facet mirror. An intermediate focus 5a of the illumination light 3 is arranged between the collector 5 and the transmission facet mirror 6. A numerical aperture of the illumination light 3 in the region of the intermediate focus 5a is, for example, NA = 0.182. Downstream of the transmission facet mirror 6 and thus the transmission optics system 4 is an illumination specification facet mirror 7, which is also referred to as a second or further facet mirror and will also be explained in more detail below. The optical components 5 to 7 are components of an illumination optics system 11 of the projection exposure system 1.

[0033] The transmission facet mirror 6 is arranged in a field plane of the illumination optics 11 in an illumination light far field of the light source 2.

[0034] The illumination preset facet mirror 7 of the illumination optics 11 is arranged at a distance from the pupil planes of the illumination optics 11. Such an arrangement is also referred to as a specular reflector.

[0035] In an alternative embodiment of the illumination optics, the second facet mirror 7 can also be arranged in a pupil plane of the illumination optics 11 and in this case is a pupil facet mirror.

[0036] Downstream of the illumination preset facet mirror 7 in the beam path of the illumination light 3 is an object to be illuminated in the form of a reticle 12, which is arranged in an object plane 9 of a downstream projection optics 10 of the projection exposure system 1. The projection optics 10 is a projection lens. The illumination optics 11 illuminates an object field 8 on the reticle 12 in the object plane 9 in a defined manner. The object field 8 simultaneously represents an illumination field of the illumination optics 11. In general, the illumination field is designed such that the object field 8 can be arranged in the illumination field.The illumination preset facet mirror 7, like the transmission facet mirror 6, is part of a pupil illumination unit of the illumination optics and serves to illuminate an entrance pupil 12a in a pupil plane 12b of the projection optics 10 with the illumination light 3 having a preset pupil intensity distribution. The entrance pupil 12a of the projection optics 10 can be arranged in the illumination beam path before the object field 8 or after the object field 8. Fig. 1 shows the case in which the entrance pupil 12a is arranged after the object field 8 in the illumination beam path. In this case, the interpupillary distance PA of the second facet mirror 7 from the pupil plane 12b results from the sum of the z-distance PA1 of the second facet mirror 7 from the object plane 9 and the z-distance PA2 of the object plane 9 from the pupil plane 12b. In the z-direction, the following applies: PA = PA1 + PA2. The interpupillary distance PA can also be measured in the beam direction.

[0037] To facilitate the representation of positional relationships, a Cartesian xyz coordinate system is used below. The x-direction in Fig. 1 runs perpendicular to the plane of the drawing. The y-direction runs to the right in Fig. 1. The z-direction runs downward in Fig. 1. The coordinate systems used in the drawing each have parallel x-axes. The course of a z-axis of these coordinate systems follows a respective main direction of the illumination light 3 within the respective figure being viewed.

[0038] The object field 8 has an arcuate or partially circular shape and is bounded by two parallel circular arcs and two straight side edges that run in the y-direction with a length yo and are spaced apart by a distance xo in the x-direction. The aspect ratio xo / yo is 13 to 1. An insert in Fig. 1 shows a plan view of the object field 8 (not to scale). One boundary shape 8a is arcuate. In an alternative and equally possible object field 8, its boundary shape is rectangular, also with an aspect ratio xo / yo.

[0039] During a projection exposure, the reticle 12 is displaced along an object displacement direction y through the object field 8.

[0040] The projection optics 10 are only partially and very schematically indicated in Fig. 1. Shown are a numerical aperture 13 on the object field side and a numerical aperture 14 on the image field side of the projection optics 10. Between the indicated optical components 15, 16 of the projection optics 10, which can be designed, for example, as mirrors reflecting the EUV illumination light 3, there are further optical components 15, 16, which are shown in Fig.

[0041] 1 not shown optical components of the projection optics 10 for guiding the illumination light 3 between these optical components 15, 16.

[0042] The projection optics 10 projects the object field 8 into an image field 17 in an image plane 18 on a wafer 19, which, like the reticle 12, is supported by a holder (not shown in detail). Both the reticle holder and the wafer holder can be displaced in both the x-direction and the y-direction via corresponding displacement drives. The installation space required by the wafer holder is shown in Fig. 1 at 20 as a rectangular box. The installation space required 20 is rectangular, with an extension in the x-, y-, and z-directions that depends on the components to be accommodated therein. The installation space requirement 20 has, for example, starting from the center of the image field 17, an extension of 1 m in the x-direction and in the y-direction. In the z-direction, the installation space requirement 20 also has an extension of, for example, 1 m starting from the image plane 18.

[0043] The illumination light 3 must be guided in the illumination optics 11 and the projection optics 10 in such a way that it is guided past the installation space requirement 20 in each case.

[0044] The transmission facet mirror 6 has a plurality of transmission facets, also referred to as first facets. The transmission facet mirror 6 can be designed as a MEMS mirror. The transmission facets are individual mirrors 21, which can be switched between at least two tilt positions and are designed as micromirrors. The individual mirrors 21 can be designed as micromirrors that can be tilted around two mutually perpendicular axes of rotation.

[0045] Of these individual mirrors 21, a row with a total of nine individual mirrors 21 is schematically shown in the yz section according to Fig. 2, which are indexed from left to right in Fig. 2 with 2h to 2b. In fact, the transmission facet mirror 6 has a significantly larger number of transmission facets 21. The transmission facets 21 are grouped into a plurality of transmission facet groups not shown in detail in Fig. 2. These transmission facet groups are also referred to as individual mirror groups, virtual field facets, or virtual facet groups.

[0046] Each of the transmission facet groups guides a portion of the illumination light 3, also referred to as an illumination light sub-beam, via an illumination channel for partial or complete illumination of the object field 8. Via this illumination channel and an illumination light sub-beam 3i guided thereover (cf. sub-beams I to IX indicated in Fig. 2), each of the individual mirror groups or transmission facet groups is assigned exactly one illumination preset facet 25 of the illumination preset facet mirror 7. In principle, each of the illumination preset facets 25 can in turn be constructed from a plurality of individual mirrors. The illumination preset facets 25 are also referred to below as second facets.

[0047] For further details of possible designs of the transmission facet mirror 6 and the projection optics 10, reference is made to WO 2010 / 099 807 A.

[0048] At least some of the illumination preset facets 25 illuminate only a sub-area or sub-field of the object field 8. These sub-fields are very individually shaped and also depend on the desired illumination direction distribution (pupil shape) in the object field 8, i.e., the illumination setting. The illumination preset facets 25 are therefore illuminated by very differently shaped virtual field facets, whose shape precisely corresponds to the shape of the respective sub-field to be illuminated. Each illumination preset facet 25 also contributes to different areas of the pupil depending on its location in the object field 8.

[0049] The illumination-presetting facet mirror 7 can be designed as a MEMS mirror, particularly if each of the illumination-presetting facets 25 is constructed from a plurality of individual mirrors. The illumination-presetting facets 25 are micromirrors that can be switched between at least two tilt positions. The illumination-presetting facets 25 are designed as micromirrors that can be continuously and independently tilted about two mutually perpendicular tilt axes, thus being able to be set to a multitude of different tilt positions.

[0050] An example of a predefined assignment of individual transmission facets 21 to the illumination preset facets 25 is shown in Fig. 2. The illumination preset facets 25 assigned to the transmission facets 2h to 2b are indexed according to this assignment. Based on this assignment, the illumination facets 25 are illuminated from left to right in the order 25e, 25s, 25s, 254, 251, 25?, 25s, 252, and 259.

[0051] The indices 6, 8, and 3 of the facets 21, 25 correspond to three illumination channels VI, VIII, and III, which illuminate three object field points OF1, OF2, OF3, numbered from left to right in Fig. 2, from a first illumination direction. The indices 4, 1, and 7 of the facets 21, 25 correspond to three further illumination channels IV, I, VII, which illuminate the three object field points OF1 to OF3 from a second illumination direction. The indices 5, 2, and 9 of the facets 21, 25 correspond to three further illumination channels V, II, IX, which illuminate the three object field points OF1 to OF3 from a third illumination direction.

[0052] The illumination directions assigned to illumination channels VI, VIII, III, illumination channels IV, I, VII, and illumination channels V, II, IX are identical. The assignment of the transmission facets 21 to the illumination preset facets 25 is therefore such that, in the illumination example shown in the figure, telecentric illumination of the object field 8 results.

[0053] The illumination of the object field 8 via the transmission facet mirror 6 and the illumination preset facet mirror 7 can be carried out in the manner of a specular reflector. The principle of the specular reflector is known from US 2006 / 0132747 A1.

[0054] Fig. 3 schematically shows a top view of a section of the first facet mirror 6 with square first facets 21 arranged in an array tilted by 45° to the xy coordinate system. The rows and columns of this array arrangement thus run at a 45° angle to the x- and y-directions, respectively.

[0055] Highlighted in Fig. 3 is a single mirror group 26 with individual mirrors 21GI to 21GII, which is imaged as the first facet into the object field 8 via a respective associated second facet 25 of the second facet mirror 15.

[0056] The individual mirrors 21G; of the individual mirror group 26 lie within an arc-shaped group boundary 27 of the individual mirror group 26. In practice, the number of individual mirrors 21G; belonging to a respective individual mirror group 26 is actually considerably larger and can, for example, be in the range between 15 and 50 or even larger. Some individual mirrors 21 of the first facet mirror 6 lie only partially within the group boundary 27. Here, by tilting the respective individual mirror 21 via a corresponding control of the illumination optics 11, a decision can be made as to whether these individual mirrors 21 lying partially within the group boundary 27 should belong to the individual mirror group 26 or not. For example, those individual mirrors 21 which are partially aligned with the group boundary 27 with at least 60% of their reflection surface or, as in Fig.3, with at least 100% of their reflection surface lying within the group boundary 27, are assigned to the individual mirror group 26. In the area, in particular, of a reflection surface proportion of 50% per individual mirror 21 that lies within the group boundary 27, there are some individual mirrors 21 that, with this selection criterion, cannot be assigned to the individual mirror group 26 highlighted in Fig. 3 or to an adjacent individual mirror group, since the reflection surface of such individual mirrors 21 lying on the boundary of the group boundary 27 does not reach the minimum surface limit within the respective group boundary 27 for any individual mirror group in the group assignment shown. Some of these individual mirrors 21 are highlighted in Fig. 3 as potential sensor individual mirrors 21s.Such potential individual sensor mirrors 21s are, as far as an image of neighboring individual mirrors 21 in the object field 8 is concerned, assigned to different field heights Xi of the individual mirror group 26, i.e. different x-coordinates of the individual mirror group 26 imaged in the object field 8. Such field heights Xi (i=l to 11) are highlighted in Fig. 3. These potential individual sensor mirrors 21s therefore represent an illumination intensity of the illumination light far field, which regularly varies only slightly over the spatial coordinates x, y of the field facet mirror 6 along an individual mirror extension, in which the field facet mirror 6 is arranged, at the location of a respective assigned field height Xi of a detection object field coordinate x.

[0057] These potential sensor individual mirrors 21s each directly border the group individual mirrors 21a of the individual mirror group 26.

[0058] Fig. 4 shows a variant of the first facet mirror 6 in a representation similar to Fig. 3. Components and functions which correspond to those already explained above with reference to Figs. 1 to 3 and in particular with reference to Fig. 3 have the same reference numerals and will not be discussed again in detail.

[0059] The field facet mirror 6 according to Fig. 4 has an array arrangement of the individual mirrors 21 that is not tilted relative to the xy coordinate system. The rows and columns of this array arrangement therefore run in the x-direction and in the y-direction.

[0060] In Fig. 4, the individual group mirrors 21a (i=1 to 18) are again highlighted. In the arrangement shown in Fig. 4, some potential individual sensor mirrors 21s and their field heights Xi (i=1 to 9) are also highlighted.

[0061] Fig. 5 shows a typical layout of an embodiment of the field facet mirror 6 with individual mirror groups 26 with respective group edges 27. These individual mirror groups 26 are arranged in the layout according to Fig. 5 in two columns of four individual mirror groups 26 each, in the manner of the individual mirror group according to Fig. 4. Fig. 5 illustrates that between two adjacent individual mirror groups 26 in one of the columns, there are individual sensor mirrors 21s at each of the field heights xi to X9 that do not belong to any of the individual mirror groups 26. A corresponding layout analogous to Fig. 5 results from an arrangement of the individual mirrors 21 tilted relative to the xy coordinate axes according to Fig. 3.

[0062] Fig. 6 shows, in a perspective, schematic view, the main components of the illumination optics 11, on the one hand, and of an intensity sensor device 31 for measuring a dependence of the intensity of the illumination light 3 incident on the object field 8 on the detection object field coordinate x, on the other hand. The intensity sensor device 31 includes selected individual sensor mirrors 2 Isi from potential individual sensor mirrors 21s, which result from individual mirrors 21 of the field facet mirror 6 that cannot be used for the individual mirror groups 26, as already explained above with reference to Figs. 3 to 5. Furthermore, the intensity sensor device 31 includes a plurality of intensity sensors 32i to 32s, which are arranged in the form of a sensor row 33 spatially adjacent to the individual mirrors 34 of the second facet mirror 7. In comparison to individual mirrors 34 of the second facet mirror 34, the intensity sensors 32i in Fig.6 are shown exaggeratedly large. The intensity sensors 32i correspond in shape and area to the second facets 25. This ensures that the light loss due to overexposure of the second facets 25 is of a similar magnitude to that due to overexposure of the intensity sensors 32i, and thus the sensor signal remains proportional to the intensity in the object field 8, even if the light loss varies over time, e.g., due to a drifting source plasma. If the second facets 25 are not physical facets of a fixed size, but virtual ones in the form of groups of second individual mirrors 34, the second facets 25 will have different shapes and sizes depending on the application. In this case, the intensity sensors 32i can also have a variable size. This can be achieved by a larger number of sensors of different sizes, additional apertures in front of the sensors, or by pixelated sensors that are only partially read out.

[0063] Fig. 6 illustrates a light path of the illumination light 3, which is guided from the light source 2 or the intermediate focus 5a via one of the individual sensor mirrors 21s, namely a sensor mirror of type 2 Isi, to the associated intensity sensor 32i.

[0064] A corresponding guidance of an illuminating light partial beam 3i from the light source 2 or the intermediate focus 5a via the individual mirror group 261 and the second facet 251 to the object field 8 is also indicated schematically.

[0065] Highlighted by appropriate hatching in Fig. 6 are two individual mirror groups 261 and 262 in the manner of the individual mirror groups 26 according to Figs. 4 and 5, which are imaged in the object field 8 via associated second facets 251, 252, superimposed on one another. In the embodiment shown, the second facets 25i each consist of a 2x2 array of the individual mirrors 34 of the second facet mirror 7. In practice, a second facet 25i can also consist of exactly one individual mirror 34 or can be constructed from a different number of individual mirrors 34, for example as a 3x3, a 4x4, a 5x5 array, a 6x6 array or even a 7x7 array. As with the individual mirror group 26 shown in Figs. 4 and 5, the individual mirror groups 26 in the illumination optics 11 shown in Fig. 6, which are imaged superimposed onto one another in the object field 8, are exactly nine individual mirrors 21 wide in the x-direction. These nine individual mirrors 21 are assigned to the field heights xi to X9.Each of the individual mirror groups 26 thus comprises individual mirrors 21 from nine adjacent individual mirror columns 1 to 9. According to this nine-column subdivision of the individual mirror groups 26 and the following field height assignment, a typification of the individual sensor mirrors 21si to 21s9 selected for applying the intensity sensors 32i to 329 results.

[0066] The individual sensor mirrors of type 2 Isi are individual mirrors 21 arranged in the same column as the individual mirrors 21 arranged in the first, left column of the respective individual mirror group 26. The individual sensor mirrors of type 2 Isi therefore belong to the field height xi.

[0067] Accordingly, the other types of individual sensor mirrors 21s2, 21s3, ... belong to individual mirrors 21 of the field facet mirror 6, which are arranged in the same columns as the individual mirrors 21 in the second, third, ... column of the respective individual mirror group 26. These other individual sensor mirrors of the types 21s2, 21s3, ... therefore belong to the field heights

[0068] X2, X3, . . .

[0069] This nine-column subdivision of the individual mirror groups 26 and the individual sensor mirrors 2 Isi enables a spatial resolution of a measurement of the dependence of the intensity of the illumination light 3 incident on the object field 8 in nine field height sections xi to X9 between a left edge xi and a right edge x rof the object field 8. These nine field height sections xi to X9 are illustrated in Fig. 6 for the object field 8. Due to the imaging, the superimposed imaging of the individual mirror groups 26 into the object field 8 results in an image inversion, so that the object field 8 in Fig. 6 appears to be curved in the opposite direction compared to the individual mirror groups 26.

[0070] The intensity sensors 32i are arranged within the sensor row 33 in the order of their assignment to the types 2 Isi of the individual sensor mirrors. This row order of the intensity sensors 32i is not mandatory; rather, only the assignment of the intensity sensors 32i to the types of the individual sensor mirrors 2 Isi, i.e., to the respective measurable field height sections xi to X9, must be known.

[0071] Using the individual sensor mirrors of type 2 Isi and the associated intensity sensor 32i, a measure of the intensity of the field height section xi of the detection object field coordinate x located on the left can be determined. The same applies to the individual sensor mirrors of types 21s2 to 21s9 and the intensity sensors 322 to 329 assigned to the field height sections X2 to X9. Using the entire sensor row 33, whose intensity sensors 32i receive the illumination light 3 of the respective type 2 Isi, the detection object field coordinate x can thus be measured across the entire object field 8 with respect to the illumination light intensity incident there.

[0072] Fig. 7 shows an assignment correlation of the individual mirror groups 26i to individual mirror columns on the field facet mirror 6. Fig. 7 shows the case, which differs from the schematic arrangement according to Figs. 5 and 6, in which a total of 8 columns of individual mirror groups 26 (j = 1 to 8) are arranged on the facet mirror 6. Shown is the dependence of a number NG of the individual mirror groups 26? on a spatial coordinate x of the field facet mirror 6. Corresponding to the eight-column arrangement, individual mirror groups 26? are present at the x-positions of the eight columns j=1 to j=8.

[0073] Fig. 8 shows, for the case of a field facet mirror 6 with a much larger number of individual mirrors 21, which deviates from the schematic representation according to Figs. 3 to 6, a distribution of potential individual sensor mirrors 21s over an entire mirror surface of the first facet mirror 6. Shown is a selection of potential individual sensor mirrors 21s for specific x-field positions, namely for a total of five exemplary x-field positions (left field edge (x=xi), field center (x=0), right field edge (x=x r ) and two more x-positions between the left field edge and the middle (x=xi / 2) and between the middle and the right field edge (x=x r / 2)).

[0074] Given the large number of individual mirror groups 26?, a distribution of the potential individual sensor mirrors 21s according to Fig. 8 results in a good statistical distribution of individual sensor mirrors 2 Isi that can be used for the intensity device 31. For each of these individual sensor mirrors 21s, the assignment of the adjacent individual mirrors 21 of the field facet mirror 6 to the respective individual mirror groups 26? determines the x-coordinate for which the respective individual sensor mirror 21s is representative when the object field 8 is illuminated by the individual mirror groups 26? adjacent to this individual sensor mirror 2 Isi. Accordingly, the respective individual sensor mirror 21s can be assigned to one of the individual sensor mirror types 2 Isi, for example, the types 2 Isi to 21s9 explained above in connection with Fig. 6.Depending on the achievable spatial resolution via the potential individual sensor mirrors 21s, the number of intensity sensors 32i of the intensity sensor device 31 can also be smaller or larger. This number i can be in the range between 3 and 100.

[0075] Fig. 9 to 11 illustrate a measurement precision of the intensity sensor device 31 in the case of an illumination light intensity that strongly depends on the detection object field coordinate x.

[0076] Fig. 9 shows, as an example, a desired target intensity distribution ISOLL, which is constant across the entire x-coordinate of the object field, in dashed lines. The solid line in Fig. 9 shows an example actual intensity distribution IIST, which has, as an example, a cosine distribution across the x-coordinate of the object field 8 and, likewise, is approximately 10% greater (more intense) than the intensity ISOLL in the area of ​​the maxima and approximately 10% smaller (less intense) than the intensity ISOLL in the area of ​​the cosine minimum.

[0077] Fig. 10 shows dashed correction measurement results I Kin which the respective x-coordinate of the object field 8, i.e. the respective field height, is assigned to the intensity sensors 32i (i=1 to 9) for the constant illumination intensity distribution ISOLL according to Fig. 9. The x-positions measured by the respective intensity sensors 32i based on the assignment to the corresponding individual sensor mirrors 2 Isi are indicated in Fig. 10 on the x-axis with the numbers "1" to "9". The dashed, measured correction intensity curve I Kof the intensity sensors 32i across the x-coordinate is not constant, unlike the constant illumination intensity ISOLL across this object field coordinate x. This corresponds to the practical situation that a cumulative intensity exposure or a number of the different types 2 Isi, to 21s9 does not have to be constant. In the realistic case shown in Fig. 10, for example, there are relatively few individual sensor mirrors of types 2 Isi, 21s?, and 21s9, so that the intensity values ​​measured there are comparatively small compared to the other measured values. These dashed correction measured values ​​I K in Fig. 10 serve as a calibration curve of the intensity sensor device 31. This calibration curve can be determined, for example, by measuring a projection exposure system in which it is ensured in another way that the object field 8 is illuminated with a homogeneous illumination intensity distribution according to the distribution ISOLL.

[0078] The measured value I is shown in Fig. 10 M of the intensity sensors 32i to 329 for the illumination intensity profile Iisr according to Fig. 9. A comparison of the dashed and the solid curve in Fig. 10 shows, even without calculating the relative changes, that the actual intensity distribution IIST is less illumination-intensive in the area of ​​the middle x-coordinates than the target distribution ISOLL and more intense in the area of ​​the left and right x-coordinate edges.

[0079] Fig. 11 shows a ratio of the measured values ​​I shown in Fig. 10 in solid and dashed lines. M and I K as a solid ratio measurement result IIST M i.e. the dashed correction values ​​I K standardized solid measured values ​​I MFig. 10. In comparison, the actual illumination intensity distribution IIST over the detection object field coordinate x is shown again in dashed lines in Fig. 11, i.e., basically the same curve that was shown in solid lines in Fig. 9. In contrast to Fig. 9, the illumination intensity distribution IIST in Fig. 11 is shown as a ratio to the target intensity distribution ISOLL. The vertical axis in Fig. 11 thus represents the ratio I M / I K or IIST / ISOL again.

[0080] Fig. 11 shows the good agreement between the measured actual value IIST M and the actual value IIST of the illumination intensity distribution over the detection object field coordinate x of the object field 8.

[0081] A deviation between these two curves IIST and IIST Mcan be a maximum of 3%, 2.5%, 2% or even smaller.

[0082] In addition, the individual sensor mirrors 21s, as illustrated in Fig. 8, can be selected such that they cover the useful range of the illumination light far field in the two far field dimensions x and y over the entire field facet mirror 6.

[0083] Due to this coverage of the useful range of the illumination light far field in the two far-field dimensions x and y by the arrangement of the usable individual sensor mirrors 21s, the far field of the light source in the arrangement plane of the field facet mirror 6 can be completely measured in two dimensions x and y by means of a corresponding embodiment of the intensity sensor device 31. Such an embodiment of the intensity sensor device 31 then has a larger number of intensity sensors 32% that cover the two-dimensionality of the far-field measurement. Such an intensity sensor device can, for example, have intensity sensors 32 f', which are arranged in an array with j rows and i columns. Since, as already explained above in connection with the sensor row 33, only the assignment of the positions of the respective individual sensor mirrors 21s to the respective intensity sensors 32 needs to be known, an array arrangement of the intensity sensors 32 does not have to correspond to the arrangement of the individual sensor mirrors 21s used for the measurement.

[0084] When measuring the dependence of the intensity of the illumination light 3 incident on the object field 8 on the detection object field coordinate x, the individual mirrors 21 of the first facet mirror 6 of the illumination optics 11 are first assigned to the individual mirror groups 26i of the first facet mirror 6 and to the second facets 25i of the second facet mirror 7, which image these individual mirror groups 26i at least in subfields of the object field 8.

[0085] Subsequently, individual mirrors 21 of the first facet mirror 6 that are not used in this assignment are selected. These selected, unused individual mirrors 21 are selected as individual sensor mirrors 21s of the intensity sensor device 31.

[0086] Subsequently, a coordinate assignment of the selected individual sensor mirrors 21s to the respective detection object field coordinate Xi takes place, into which the individual mirrors 21 of the first facet mirror 6 directly adjacent to the individual sensor mirrors 21s to be assigned are imaged into the object field 8. This corresponds to an assignment of the respective individual sensor mirror 21s to a single sensor mirror type 2 Isi, as explained above.

[0087] Now, depending on the coordinate assignment performed, one of the intensity sensors 32i is assigned to the individual sensor mirror 32si assigned to the respective detection object field coordinate Xi. Now, a portion of the illumination light 3 is guided as detection illumination light via the individual sensor mirror 2 Isi assigned to the respective detection object field coordinate or the field height section Xi to the assigned intensity sensor 32i. This can be done parallel to the projection exposure. Sensor data from the intensity sensors 32i exposed to the detection illumination light are now evaluated to determine the dependence of the intensity l of the illumination light 3 incident on the object field 8 on the at least one detection object field coordinate x.

[0088] This sensor data evaluation can be followed by a correction of the intensity dependence of the illumination intensity on the detection object field coordinate x, for example by changing an assignment of the individual mirrors 21 of the first facet mirror 6 to the respective individual mirror groups 26i or by changing an assignment of the individual mirror groups 26i to the second facets 25i.

[0089] The projection exposure can be carried out parallel to the measurement or after an appropriate correction.

[0090] The selection and assignment of the individual sensor mirrors 21s and an evaluation of the sensor data can be carried out in such a way that a 2D far-field measurement results from the evaluated sensor data. The respective data of the selected and assigned individual sensor mirrors 21s can form support points of a measuring far-field, between which the entire measuring far-field is then deduced by extrapolation. To produce a microstructured component, in particular a highly integrated semiconductor device, for example a memory chip, with the aid of the projection exposure system 1, the reticle 12 and the wafer 19 are first prepared. Subsequently, a structure on the reticle 12 is illuminated with the illumination light 3 using the illumination optics 11 and projected onto a light-sensitive layer on the wafer 19 using the projection optics of the projection exposure system 1.By developing the light-sensitive layer, a microstructure is then created on the wafer 19 and from this the micro- or nano-structured component is created.

[0091] The component produced may be a microchip, in particular a memory chip.

Claims

Patent claims 1. Illumination optics (11) with a first facet mirror (6) with first individual mirrors (21) for reflecting the illumination light (3) of an EUV light source (2) and for arrangement in a useful area of ​​an illumination light field, with a second facet mirror (7) for reflecting the illumination light (3) reflected by the first facet mirror (6) towards an object field (8) in which an object (12) to be illuminated can be arranged, wherein the second facet mirror (7) has second individual mirrors (34) forming second facets (25) which, via partial beams (3i) of the illumination light (3), image individual mirror groups (26) of the first facet mirror (6), forming first facets, at least in partial fields of the object field (8), with an intensity sensor device (31) for measuring a dependence of an intensity (IIST) of the illumination light (3) on the object field (8) incident illumination light (3) from at least one detection object field coordinate (x),wherein the intensity sensor device (31) comprises:, — a plurality of the first individual mirrors, which represent individual sensor mirrors (21s) of the first facet mirror (6), wherein the individual sensor mirrors (21s) are assigned to several different object field positions (xi) along the detection object field coordinate (x), — a plurality of intensity sensors (32i), wherein the individual sensor mirrors (21s) are designed to reflect the illumination light (3) towards the intensity sensors (320).

2. Illumination optics according to claim 1, characterized in that the number of intensity sensors (32i) is in the range between 3 and 100.

3. Illumination optics according to claim 1 or 2, characterized in that the intensity sensors (32i) are arranged spatially adjacent to the second individual mirrors (34) of the second facet mirror (7).

4. Illumination optics according to one of claims 1 to 3, characterized in that the intensity sensors (32i) are arranged as a sensor line (33).

5. Illumination optics according to one of claims 1 to 4, characterized in that the individual sensor mirrors (21s) are arranged on the first facet mirror (6) in such a way that they cover the useful range of the illumination light far field in two far field dimensions (x, y).

6. Method for measuring a dependence of an intensity (IIST) of the illumination light (3) incident on the object field (8) on at least one detection object field coordinate (x) using an illumination optics (11) according to one of claims 1 to 5, comprising the following steps: Assigning the individual mirrors (21) of the first facet mirror (6) of the illumination optics (11) to the individual mirror groups (260) of the first facet mirror (6) which form the first facets, to the second facets (25i) of the second facet mirror (7) which form these Single mirror groups (260) image at least in subfields of the object field (8), Selecting individual mirrors (21) of the first facet mirror (6) not used in the assignment as individual sensor mirrors (21s) of the intensity sensor device (31), Coordinate assignment of the selected individual sensor mirrors (21s) to detection object field coordinates (x0, into which the individual mirrors (21) of the first facet mirror (6) directly adjacent to the individual sensor mirrors (21s) are imaged in the object field (8), sensor assignment, depending on the coordinate assignment, of one of the intensity sensors (32i) to the individual sensor mirror (21s) assigned to the respective detection object field coordinate (x), and guiding detection illumination light (3) via the individual sensor mirror (21s) assigned to the respective detection object field coordinate (x0) to the assigned intensity sensor (320, Evaluating sensor data of the intensity sensors (320) exposed to the detection illumination light (3) to determine the dependence of the intensity (IIST) of the illumination light (3) impinging on the object field (8) on the at least one detection object field coordinate (x).

7. Method according to claim 6, characterized by selecting and assigning the individual sensor mirrors (21s) and evaluating the sensor data such that a 2D far-field measurement of the illumination light far-field results from the evaluated sensor data.

8. Illumination system with an illumination optics (11) according to one of claims 1 to 5 and with an EUV light source (2).

9. Optical system with an illumination optics (11) according to one of claims 1 to 5 and with a projection optics (10) for imaging the object field (8) in an image field (17).

10. Projection exposure system with an optical system according to claim 9 and with an EUV light source (2).

11. Process for producing a micro- or nano-structured component with the following process steps: Providing a reticle (12), Providing a wafer (19) with a coating sensitive to the illumination light (3), Projecting at least a portion of the reticle (12) onto the wafer (19) using the illumination exposure system (1) according to claim 10, Developing the light-sensitive layer on the wafer (19) exposed to the illuminating light (3).

12. Component manufactured by a method according to claim 11.

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