Configurations, methods, and computer program products for system integrated calibration of facet mirrors in microlithographic illumination systems

Abstract

The present invention relates to a configuration (100), a method and a computer program product for system integrated calibration of facet mirrors (18, 19) in a microlithographic illumination system (20). According to the invention, calibration beam paths (103, 104) guided via facet mirrors (18, 19) between the calibration radiation source device (101) and the calibration radiation sensor device (102) are defined, only one pivotable micromirror (18 ') in a single facet mirror (18) consisting of micromirrors (18') being involved in each of the calibration beam paths. By pivoting a micromirror (18 ') involved in a defined calibration beam path (103, 104), a specific optimal pivot position can be found based on the calibration radiation sensor device (102), the basic orientation of which micromirror (18') can also be derived by geometric calculations. The orientation sensor of the micromirror (18 ') of the facet mirror (18) can be calibrated by comparing the calculated orientation with the orientation determined by the orientation sensor at the micromirror (18').

Description

[0001] This application claims the priority of German Patent Application No. 10 2022 210 158.8 filed on September 26, 2022. The contents of this German Patent Application are incorporated by reference into this application for reference. Technical Field

[0002] The present invention relates to arrangements, methods and computer program products for system-integrated calibration of facet mirrors in microlithography illumination systems. Background Art

[0003] Microlithography is used to produce microstructured components, such as, for example, integrated circuits. The projection exposure apparatus used in the process comprises an illumination system and a projection system. An image of a mask (also called a reticle) illuminated by means of the illumination system is projected by the projection system in a reduced size onto a substrate (e.g. a silicon wafer) coated with a photosensitive layer and arranged in the image plane of the projection system, so that the mask structure is transferred to the photosensitive coating of the substrate.

[0004] Typically, two facet mirrors are arranged in the beam path between the actual exposure radiation source and the mask to be illuminated in the case of an illumination system (in particular an illumination system designed for the EUV range, that is to say for a projection exposure apparatus with an exposure wavelength from 5 nm to 30 nm), and the mirrors homogenize the radiation in a manner substantially comparable to the fly-eye condenser principle. The closer facet mirror in the beam path of the exposure radiation source is typically a so-called field facet mirror, while the other facet mirror is a so-called pupil facet mirror.

[0005] In order to be able to generate different intensity and / or angle of incidence distributions during the illumination of the reticle, it is known that the facets of one of the two facet mirrors, in particular the facets of the field facet mirror, are formed by electromechanically pivotable micromirrors. Although it may be known in the prior art to form the two facet mirrors by corresponding micromirrors, it is sufficient for a large number of intended uses if the respective other facet mirror, i.e. in particular the pupil facet mirror, has fixed facets or facets which are adjustable (in particular tiltable) only between two defined positions, i.e. a reflecting position and a non-reflecting position. If only one of the two facet mirrors is formed by a micromirror, the complexity of the illumination system and in particular the complexity of its control is relatively reduced.

[0006] In order to achieve the required accuracy when setting the desired intensity and angle of incidence distribution, it is in principle necessary to be able to precisely set the orientation of the individual micromirrors of the faceted mirror constructed therefrom. In this case, the micromirrors also contain orientation sensors, with which the orientation of the micromirrors can be read and verified in essentially two spatial directions, in addition to the microelectromechanical drives required for pivoting the mirrors.

[0007] The relationship between the actual orientation of a micromirror and the values ​​determined by the orientation sensor is usually nonlinear and requires calibration, the latter generating a sensor characteristic curve which exhibits the values ​​determined by the orientation sensor and can in fact be used to control the micromirror in the first place. Here, accuracies of the order of 10 μrad are required in microlithography applications.

[0008] It has been found that the sensor characteristic curve of the orientation sensor drifts and other similar changes may occur, so that the accuracy of the orientation of the micromirrors determined by the orientation sensor decreases over time and thus the setting accuracy of the intensity and angle of incidence distribution also decreases.

[0009] Therefore, the continuous operation of an illumination system comprising a faceted mirror consisting of motor-pivotable micromirrors requires regular recalibration. However, known calibration methods requiring opening of the illumination system and / or application of external measuring sensor systems are complex and time-consuming.

[0010] Further calibration methods are described in the published applications DE 10 2015 219 447 A1 and DE 10 2019 204 165 A1 and in the not yet published German patent application 10 2022 203 369.8. Summary of the invention

[0011] The invention is based on providing an arrangement, a method and a computer program product for system-integrated calibration of facet mirrors in microlithography illumination systems, which allow performing the discussed recalibration in a system-integrated manner, i.e. without using an external measurement sensor system and preferably without opening the illumination system.

[0012] This object is achieved by an arrangement as claimed in claim 1, a method as claimed in claim 11 and a computer program product as claimed in claim 19. The dependent claims relate to advantageous developments.

[0013] The invention therefore relates to an arrangement for system-integrated calibration of facet mirrors of a microlithography illumination system, wherein the facet mirror to be calibrated is configured as a micro-electromechanical system with a plurality of individually pivotable micro-mirrors, said micro-mirrors having respective orientation sensors for determining the orientation of the micro-mirrors, and the facet mirror is arranged fixedly positioned in a beam path of an illumination optics unit of the illumination system, such that a beam emanating from an exposure radiation source is deflected by the exposure optics unit onto a reticle plane of the illumination system, the exposure optics unit comprising the facet mirror to be calibrated and a further facet mirror without the micro-electromechanical system, wherein at least one calibration radiation source arrangement and at least one calibration radiation sensor arrangement are provided, wherein one arrangement is arranged in the vicinity of the reticle plane of the illumination system, remote from an area provided for the reticle and its exposure, and the further arrangement is arranged in such a way that, given a suitable pivot position of the micro-mirrors, at least one calibration beam path emanates from the calibration radiation source(s) or one of them, via a predefined micro-mirror of the facet mirror to be calibrated, and a predefined facet of another facet mirror of the calibration radiation sensor(s) or one of them is definable.

[0014] Furthermore, the invention relates to a method for calibrating a facet mirror, which is formed by micromirrors in a microlithography illumination system using an arrangement according to the invention, the method comprising the following steps:

[0015] a) pivoting a micromirror of a facet mirror constructed therefrom, the micromirror being involved in a defined calibration beam path from a calibration radiation source device via an illumination optical unit comprising at least two facet mirrors to a calibration radiation sensor device, at least over a pivot axis range, wherein the calibration beam path is incident on the calibration radiation sensor device and is detected by the latter;

[0016] b) determining, by means of the calibration radiation sensor arrangement, an optimum pivot position of the pivoting micromirror, in which case the calibration beam path is incident on the radiation detector as optimally as possible;

[0017] c) determining the orientation of the micro-mirror by an orientation sensor of the pivotable micro-mirror for determining an optimal pivoting position;

[0018] d) comparing the orientation determined by the orientation sensor of the pivoted micro-mirror with the orientation calculated from the defined calibration beam path; and

[0019] e) Recalibrating the orientation sensor of the micromirror based on the comparison performed.

[0020] Finally, the invention also relates to a computer program product or a set of computer program products comprising program portions designed to carry out the method according to the invention when loaded into a computer or a networked computer connected to the configuration according to the invention.

[0021] First, some terms used in the disclosure of the present invention are explained:

[0022] The term "micromirror" denotes a small, in particular rectangular, mirror with an edge length of at most 1 mm x 1 mm, 1.5 mm x 1.5 mm or 2 mm x 2 mm. If the micromirror itself is not rectangular, the smallest rectangle surrounding it has the mentioned dimensions.

[0023] A "micro-electromechanical system (MEMS)" for the facet mirror comprises an orientation sensor and also an actuator to enable the micro-mirrors of the facet mirror to be individually pivoted. In particular, a micro-electromechanical system can be realized using microsystems technology.

[0024] The term "pivoting" relates to the possibility of setting the orientation of the micromirror within the pivoting range according to actual requirements. In this case, pivoting is particularly possible about two non-parallel axes, thus resulting in, for example, a conical or pyramidal pivoting range. Preferably, the pivoting is carried out systematically, that is, the micromirror is controlled in a targeted manner so that it pivots according to a predetermined movement pattern for the pivoting movement.

[0025] In principle, an "orientation sensor" makes it possible to unambiguously determine the orientation of a micromirror. If the micromirror can be pivoted in two directions, the orientation sensor will usually also generate two values, each reflecting the pivot position in one direction. For example, the orientation sensor can be of capacitive design, in which case, for example, the capacitance of two mutually meshing combs is measured, one of which is stationary and the other moves with the micromirror. The measured capacitance then reflects the pivot position of the micromirror.

[0026] "Calibration of a facet mirror" means a process which aims to ensure that, in the case of a predefined angular position by means of a suitable signal for a specific micro-reflector, this angular position is actually also adopted by the corresponding micro-reflector. In particular, if the actual angular position of a micro-reflector can be verified here by means of an orientation sensor, the calibration of the facet mirror in principle covers in particular the calibration of the orientation sensor. In this case, "calibration" generally means that a predefined conversion function of a first measured value is adapted to a measured variable reflecting a second measurable value. Thus, in the case of an orientation sensor of a micro-reflector, an analog electrical or digital signal or a plurality of analog electrical or digital signals are converted into an angular specification or a plurality of angular specifications, for example, by means of a conversion function adapted by calibration, which reflects the orientation of the micro-reflector relative to a defined zero orientation. According to the conversion function, in particular according to the number of its variable parameters, it is advantageous to perform a plurality of measurements of the first value for different second values ​​for the purpose of complete calibration, in order to be able to have a sufficient number of supporting points to fully adapt the conversion function or all its parameters. In this context, the basic goal of calibration is to adapt the conversion function accurately enough so that the measured variable determined from the first measured value corresponds as accurately as possible to the actual second value, without having to measure the second value itself. Often, there are even provisions for an accuracy to be achieved by means of the calibration, which accuracy should be achieved over the entire value range or a specified part of the value range of the first measured value.

[0027] Before performing the actual calibration to obtain the specified accuracy, some kind of "basic calibration" is assumed (optionally still requiring verification or verifiability), or a basic calibration is performed. In the "basic calibration" there is also an adaptive transfer function, which is also adapted during the actual calibration; the transfer functions of the basic calibration and the actual calibration are often even identical. However, the accuracy of the transfer function with the basic calibration is often orders of magnitude lower than that of the subsequent full calibration. However, it is helpful as a starting point for the actual calibration, because the basic calibration is at least in the vicinity of the final desired calibration, thus allowing a lower effort for the actual calibration.

[0028] If one or more facets of the facet mirror are configured to be only "tiltable", the facet, in particular its reflective surface, can be moved between two defined end positions, i.e., in principle, positions in which the facet can participate in the beam path from the exposure source and the reticle plane, as well as positions in which this is not the case. Optionally, discrete intermediate positions can also be defined. Even if a corresponding situation similar to a pivoting movement can be achieved, such a tilting movement still does not include a pivoting within the meaning of the present invention, since it is in principle not possible to achieve a targeted adoption of any desired intermediate position between the previously defined end positions and / or discrete intermediate positions. Therefore, tiltable facets usually also do not have such orientation sensors provided to the micromirrors.

[0029] A device is located "near a plane" if the distance between the device and the plane is up to 500 mm, preferably up to 200 mm, more preferably up to 100 mm. It goes without saying that this term also covers here the configuration of the device directly in the plane, i.e. at a distance of 0 mm from the plane. If the device has a large range in the distance direction, relevant surfaces of the device, in particular the active surface, can also be used to determine the distance between the device and the plane. The active surface can be, for example, a sensor surface in the case of a sensor device and, for example, a radiation exit surface in the case of a radiation source device.

[0030] A device is considered to be configured "planar" if its relevant surface, in particular the active surface, has a larger two-dimensional extent than in conventional non-planar construction variants. For example, a radiation source device or its exit surface is considered to be planar if, when viewed by a person skilled in the art, the radiation source is no longer considered point-shaped in the sense of point light. A sensor or its sensor surface is considered to be planar if, when the sensor is triggered, the position of incidence on the sensor surface cannot be meaningfully at least approximately equal to the position of the sensor surface itself. In conjunction with the present invention, a planar construction exists, for example, in particular if the device in question or its relevant, in particular active surface or a rectangle enclosed by this surface is larger than 2 mm x 5 mm, 4 mm x 50 mm or 10 mm x 100 mm.

[0031] The invention has recognized that it is possible to calibrate, in particular recalibrate, a facet mirror consisting of pivotable micromirrors in an illumination system in a system-integrated manner, i.e., for example, to improve the accuracy of the sensor characteristic curve of individual micromirrors in a facet mirror which is usable in principle but may no longer be accurate due to drift, if necessary, by only minimal changes to the known illumination system, in the extreme case by only providing a single calibrated radiation sensor device in the reticle plane. In particular, no additional moving parts need to be provided for this purpose.

[0032] The invention makes use of the high-precision positioning fixed arrangement of two facet mirrors, which are usually required for illumination in the field of microlithography, and whose geometrical shape and optical properties are likewise known, in order to generate a calibration beam path from a calibration radiation source device to a calibration radiation sensor device by appropriately pivoting one of the micromirrors of the facet mirror constructed therefrom, in which the other facet mirror, only the pivoted micromirror of the facet mirror consisting of micromirrors (mentioned for this purpose), is included. In order to ensure this, the remaining micromirrors of the facet mirror concerned should usually be oriented so that the beam path passing through it (if appropriate) is absolutely not incident on the calibration radiation sensor. It goes without saying that any desired further optical components, such as additional fixed deflection mirrors, etc., can also be included in the calibration beam path.

[0033] In this case, the further facet mirror is a facet mirror without microelectromechanically pivotable micromirrors.For example, the further facet mirror can thus exclusively have fixed and / or only tiltable facets.

[0034] Since the device(s) arranged near the reticle plane are arranged away from the area in which the reticle is arranged or at least the area in which the reticle is illuminated, and furthermore no structural changes to the facet mirrors are required, the basic functionality of the illumination system is not restricted. By appropriately pivoting the micromirrors of the facet mirrors constructed therefrom, known exposure scenarios for the reticle arranged in the reticle plane can also be realized. Of course, it is assumed here that the device(s) not arranged near the reticle plane in the configuration according to the invention also do not restrict the basic functionality of the illumination system, for example by shadowcasting or the like. In principle, the micromirrors can even be calibrated in parallel with the illumination of the reticle, i.e. specifically, the beam path through the micromirrors is incident on the calibration radiation sensor as a calibration beam path. In this case, the area provided to the reticle in the reticle plane also particularly includes areas in which the reticle is not permanently arranged, but only occurs from time to time, for example due to a displacement of the reticle in the so-called scanning direction.

[0035] For the beam path provided according to the invention, it is possible on the one hand to mathematically determine the optimal orientation of the micromirror to be calibrated. For this purpose, in addition to knowing the configuration and properties of the components of the illumination system, in particular the facet mirrors, it is usually necessary to know only the position and possible orientation of the calibration radiation source device and / or calibration radiation sensor device contained in the beam path relative to the illumination system or its components. Depending on the construction and configuration of the calibration radiation source device and / or calibration radiation sensor device concerned, the position of at least one of the devices must be known exactly, while the position of the other device may not need to be known, or at least not exactly.

[0036] On the other hand, by pivoting the relevant micromirror in the beam path and observing the signal of the calibration radiation sensor device, the pivoting range of the micromirror can be "scanned" until, for example, the maximum possible intensity is established at the calibration radiation sensor device, or the beam path is incident at a predetermined point on the calibration radiation sensor device, where the desired optimal pivot position of the micromirror is usually obtained. By comparing the micromirror orientation determined by the orientation sensor with the optimal pivot position found by the arithmetically determined optimal orientation, the orientation sensor can be calibrated at least for this specific orientation.

[0037] If this process is repeated for a specific micromirror with a sufficient number of different beam paths, each requiring a different micromirror orientation, this results in a corresponding number of support points which allow a sufficiently accurate calibration of the orientation sensor over the entire pivot range. However, depending on which facet mirror is constructed from the micromirrors, more than one calibration radiation source device and / or more than one calibration radiation sensor device may be required here in order to be able to obtain the corresponding different beam paths. Alternatively or additionally, the device (particularly arranged near the reticle plane) can also be arranged in a planar manner. A corresponding construction in principle increases the number of possible calibration beam paths, from which a specific calibration beam can then be selected.

[0038] The calibration radiation sensor device(s) or at least one of them may be an intensity detector, that is to say a detector operable to measure the intensity of radiation incident across a detector surface within a wavelength range accessible by the detector. A stop may be provided to clearly define the detector surface relevant for the intensity measurement.

[0039] The calibration radiation sensor device(s) or at least one of them may also comprise a one-dimensional or two-dimensional array sensor, such as a CCD array sensor or an active pixel sensor. With a one-dimensional array sensor, the position of incidence of radiation on the array sensor may be determined in a one-dimensional direction, wherein in the case of a desired planar configuration, the array sensor may extend in a direction perpendicular thereto. For a two-dimensional array sensor, which is itself planar, the two-dimensionality of the active sensor surface may also allow the regularity of the position of the center point of maximum intensity on the sensor surface, thereby determining the point of incidence of the beam path in addition to the intensity of the radiation incident on the sensor, which may further increase the calibration accuracy if the configuration of the sensor is known exactly. If the calibration radiation sensor device or its sensor has appropriate dimensions, a plurality of beam paths may also be incident on the calibration radiation sensor device simultaneously at a sufficient distance, whereby a parallel calibration of a plurality of micromirrors becomes possible. In principle, this is already true for a configuration with a one-dimensional array sensor, but in particular for a configuration with a two-dimensional array sensor.

[0040] In principle, the optimal pivot position of the micromirror for a defined beam path can also be determined based on the pivot range, even for the radiation incident on the calibration radiation sensor device, if a constant (mis)calibration over the entire pivot range is assumed. If the contour of the pivot range in question is thus determined, the optimal pivot position can be determined geometrically. In this case, the calibration radiation sensor device(s) or even at least one of them can be a binary detector, which only specifies whether radiation emitted from one of the calibration radiation source devices(s) is incident on this detector.

[0041] The calibration radiation sensor arrangement(s) or at least one of them may further comprise a narrowband wavelength filter adapted to the wavelength of at least a part of the calibration radiation source arrangement(s). This may reduce possible falsification of the measurement results of the respective calibration radiation sensor by stray radiation not originating from any of these calibration radiation source arrangements, such as stray radiation emitted from an exposure radiation source of the illumination system.

[0042] In principle, the exposure radiation source of the illumination system itself can be used as the calibration radiation source device or one of a plurality of calibration radiation source devices. The exposure radiation source can also be an EUV exposure radiation source in particular. The calibration radiation sensor device(s) provided for detecting the beam path emanating from such a calibration radiation source device must then be designed for detecting radiation in the corresponding wavelength range.

[0043] It is also possible that the one or more calibration radiation source devices are each individual radiation sources, which are preferably arranged in the region of the intermediate focus of the exposure radiation source, i.e. in particular near or in the intermediate focus. The corresponding individual radiation source preferably emits light in the visible range. For this purpose, the radiation source can, for example, comprise a high-power light-emitting diode, for example with a light output in the wavelength range from 400 nm to 500 nm and a radiation flux of from 500 mW to 1.5 W for a light-emitting area in the range from 0.5 mm x 0.5 mm to 2 mm x 2 mm, or a laser as the actual light source, which is however preferably arranged in a fiber-coupled manner and at a distance from the actual position of the radiation source, so that the radiation source or the light exit opening of the coupled fiber can be arranged in a space-saving manner inside the illumination system and as little heat as possible is introduced into the illumination system.

[0044] As described by way of example above, the number, configuration and / or construction of at least one calibration radiation source device and / or at least one calibration radiation sensor device are preferably selected in such a way that at least one, preferably at least three, preferably at least five calibration beam paths can be defined for at least a portion of, preferably for each micro-reflector in a faceted mirror constructed thereby. If a corresponding calibration beam path is defined for each micro-reflector, a minimum calibrability of each micro-reflector is provided. Given at least three or five calibration beam paths for at least a portion of a micro-reflector, the minimum number of support points generally required for sufficiently accurate calibration of an orientation sensor in a micro-reflector can be obtained. However, more calibration beam paths are usually defined, for example nine or more. With a corresponding increase in the number of support points used for calibration, the calibration accuracy of the micro-reflector can usually be further improved.

[0045] If more than one device, i.e. a calibration radiation source device or a calibration radiation sensor device, is arranged near the reticle plane, it is preferred that these devices are arranged near the reticle plane on both sides of the area provided for exposing the reticle. If the reticle is displaceable in the scanning direction, the device(s) are preferably arranged in such a way that the displaceability of the reticle is not restricted by the devices.

[0046] The arrangement according to the invention is particularly suitable for illumination systems in which the facet mirror to be calibrated is a field facet mirror for forming one or more virtual light sources on a pupil facet mirror arranged downstream in the beam path and having fixed or merely tiltable facets. The virtual light sources are one or more image representations of real exposure radiation sources, which, however, can be regarded as respective independent light sources in the further processing of the exposure and projection optical units.

[0047] Preferably, the micro-mirrors of the faceted mirror are each pivotable about two non-parallel axes, preferably mutually perpendicular axes, so that the normal vector of the mirror can sweep through a two-dimensional angular space, usually in a conical or pyramidal manner. When illuminating the reticle, the corresponding micro-mirrors allow a large variation in the intensity distribution.

[0048] Further details about the arrangement according to the invention can also emerge from the following explanation about the method according to the invention regarding the system-integrated calibration of a facet mirror of a microlithography illumination system, which is achieved by means of the arrangement according to the invention.

[0049] The method according to the invention is based on a calibration beam path defined at the outset, which proceeds from a predefined calibration radiation source arrangement through the exposure optical unit (i.e. in particular also or at least via two facet mirrors, at least one of which is formed by a micromirror) to a predefined calibration radiation sensor arrangement. In particular, taking into account the highly precise positional fixed arrangement of the individual components in the microlithography illumination system and their corresponding known optical properties, the corresponding beam path can usually be defined without problems.

[0050] If there is a defined calibration beam path, the individual micromirrors participating in this calibration beam path can be pivoted particularly systematically and the signals of the calibration radiation sensor device observed until the orientation of the micromirrors corresponds to the orientation provided for the defined calibration beam path. Specifically, the particularly systematic pivoting means that the beam path emanating from the micromirrors may not or only partially impinge on downstream optical components such as, for example, fixed or only tiltable facets of a downstream facet mirror, thus resulting in losses in the event that radiation eventually reaches the calibration radiation sensor, and / or the beam path may not impinge on the calibration radiation sensor device, only partially impinge on it or, in the case of a configuration as an array sensor, at least not impinge on it at the intended position of the defined calibration beam. At least when the actual orientation of the micromirrors corresponds to the orientation provided for the defined calibration beam, a signal indicating this with sufficient certainty can be acquired at the calibration radiation sensor device. In this case, the particularly systematic pivoting of the micromirrors can limit the pivoting range in which the calibration beam path is actually incident on the calibration radiation sensor device and can in principle be detected by it.

[0051] The particular systematic pivoting of the micromirrors is preferably carried out assuming a certain basic calibration. If a suitable basic calibration is assumed, then in the case of the calibration radiation sensor device detecting the calibration radiation it can be assumed that the incident radiation actually reaches the calibration radiation sensor device according to the defined calibration beam path and not, for example, due to reflections from facets provided by the defined calibration beam path in the facet mirrors formed by the micromirrors. If a corresponding basic calibration cannot be assumed, for example, all facet mirrors which are not involved in the defined calibration beam path can be tilted, if possible, so that the beam path can no longer reach the calibration sensor via them. Alternatively, the basic calibration can be determined by movement into end positions of the microelectromechanical adjustment of the micromirrors and the orientation determined by the orientation sensor for these positions.

[0052] A particularly systematic pivoting of the micromirror makes it possible to determine an optimal pivot position. Specifically, the optimal pivot position is the position at which the calibration beam path is incident on the calibration radiation sensor device as best as possible. In this case, the way in which the calibration beam path can be incident on the calibration radiation sensor device "as best as possible" depends on the configuration of the latter.

[0053] In the case of a binary calibration radiation sensor device, which can only determine whether radiation is incident on it, it can, for example, determine the limits of the pivot range within which the calibration radiation still impinges on the calibration radiation sensor device, and from which the optimal pivot position can be calculated by geometric considerations, and can subsequently be moved to this position in order to read out the orientation determined by the orientation sensor for this pivot position.

[0054] If the calibration radiation sensor device is an intensity detector, the optimal pivot position usually exists when the measured intensity is at a maximum. If during the recording of the intensity in the orientation determined by the orientation sensor, a clear maximum cannot be determined directly, for example because a plateau of maximum intensity has been determined, the central maximum of the intensity determined by the radiation detector, the slope of the intensity rise and fall during a particularly systematic pivoting of the micromirror, and / or the centroid of the corresponding intensity distribution can also be used to determine the optimal pivot position.

[0055] If the calibration radiation sensor device concerned in the calibration beam path is a one-dimensional or two-dimensional array sensor - optionally in addition to the intensity, an optimal pivot position exists when the beam path or the center point of this beam path incident on the sensor is incident at the expected position based on the defined calibration beam path. In principle, the micromirror can be pivoted in a particularly systematic manner until the calibration beam actually impinges on the calibration radiation sensor at the expected position; however, in the case of an incident position deviating from its position, the instantaneous actual orientation of the micromirror can also be determined by calculation and used as the basis for the subsequent calibration instead of the orientation based on the defined calibration beam path. The beam path or the center point of this beam path incident on the sensor can also be incident at the expected position of a plurality of different pivot positions. However, the optimal pivot position can then usually be determined by means of a measured pivot position profile for which the beam path is incident on the sensor.

[0056] Once the optimal pivot position of the micromirror has been determined, the orientation determined by the orientation sensor for the pivot position can be determined. In this case, the micromirror can in principle be pivoted to the pivot position determined to be optimal and the orientation determined by the orientation sensor can then be read. However, it is preferred that the orientation determined by the orientation sensor is recorded in addition to the values ​​of the radiation sensor during a particularly systematic pivoting of the micromirror. Once the optimal pivot position has been determined, the matching orientation determined by the orientation sensor can be read directly from the recorded data.

[0057] The orientation of the optimal pivot position of the defined calibration beam path, which orientation has been determined in this way by means of an orientation sensor of a specially systematically pivoted micromirror, can be compared with the optimal orientation which can be calculated from the defined calibration beam path in order to determine thereby whether the current calibration of the orientation sensor is still correct or whether there is a deviation between the orientation determined by the orientation sensor and the value calculated based on the defined calibration beam path, which requires recalibration.

[0058] In this case, the procedure from the particularly systematic pivoting of the micromirror (step a) to the comparison of the orientation determined by the orientation sensor with the calculated orientation (step d) can be carried out simultaneously for all axes about which the micromirror can be pivoted. However, it is also possible to carry out the method steps in question individually, in particular in direct succession, for each of these axes.

[0059] If steps a) to d) from the particularly systematic pivoting of the micromirror to the comparison of the orientation determined by the orientation sensor with the calculated orientation are performed for a single calibration beam path, the calibration of the micromirror can be verified for a specific pivot position of the micromirror. However, in view of the regular nonlinear relationship between the signal of the orientation sensor and the orientation of the micromirror, it is preferred that steps a) to d) for the particularly systematic pivoting of the micromirror are performed by at least three, preferably at least five, more preferably at least nine different defined calibration beam paths. However, for reliable and accurate calibration of the micromirror, steps a) to d) can also be performed with 20, 50 or 100 different beam paths.

[0060] If the comparison according to step d) has been carried out for all calibration beam paths provided for the micromirrors to be adjusted, the data from at least one comparison can be used to recalibrate the orientation sensor of the micromirrors. In other words, the sensor characteristic curve of this orientation sensor is adjusted in such a way that the value determined by the orientation sensor of the micromirrors corresponds as accurately as possible to the actual orientation of the respective micromirrors, but in particular with a desired accuracy. The desired accuracy can be defined, for example, as a maximum of 50 μrad, a maximum of 20 μrad or a maximum of 10 μrad.

[0061] During this recalibration, in particular an n-dimensional characteristic curve of the tilt sensor can be adapted, where n corresponds to the number of axes about which the associated micromirror can pivot. Depending on the shape of this n-dimensional characteristic curve, steps a) to d) should be performed with a sufficient number of different beam paths to obtain a suitable number of support points for recalibrating or adapting the characteristic curve.

[0062] In principle, the method according to the invention and the configuration according to the invention respectively allow to calibrate individual micromirrors in parallel with the microlithographic exposure by means of the remaining micromirrors of the facet mirror. In view of the usually large number of micromirrors and the time usually required for calibrating a single micromirror, it is even preferred to perform the calibration in parallel with the actual exposure in order to minimize downtimes of the illumination system and therefore of the entire microlithographic projection exposure apparatus due to calibration.

[0063] In order to keep any possible mutual interference of exposure and calibration as small as possible, it is preferred that the calibration radiation source device(s) which is different from the exposure radiation source of the illumination system is spectrally and / or temporally decoupled from the exposure of the exposure radiation source. If a calibration radiation source device(s) which is different from the exposure radiation source is used, a suitable choice of the calibration radiation source device(s) may ensure that the latter emits or does not emit radiation in a wavelength range relevant for the exposure. Thereby and due to the possible provision of suitable wavelength filters at the calibration radiation sensor device, interference with the calibration due to radiation emitted from the exposure radiation source may also be at least reduced.

[0064] Furthermore, the exposure radiation sources used in microlithography are usually operated in a pulsed manner. Therefore, the calibration radiation source arrangement(s) provided for calibration purposes may be operated only when the exposure radiation source does not emit any radiation. In other words, the calibration radiation source arrangement provided for calibration may be operated in an offset pulsed manner relative to the exposure radiation source.

[0065] The arrangement according to the invention preferably comprises a control device designed to carry out the method according to the invention. In particular, this can be an existing control device of an illumination system designed according to the invention, or a control device of a microlithography projection exposure apparatus in which the illumination system is embedded.

[0066] The computer program product according to the invention comprises a program portion which, when loaded into a suitable control device, is designed to carry out the method according to the invention. This is particularly relevant for microlithography projection exposure apparatus which, for other reasons, has a configuration comparable to that according to the invention and which therefore does not require further structural modifications for the purpose of carrying out the method according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The invention will now be described based on advantageous specific embodiment examples with reference to the accompanying drawings, in which:

[0068] Figure 1 A schematic diagram showing a microlithographic projection exposure apparatus comprising an arrangement according to the invention;

[0069] Figure 2 Displayed by Figure 1 A sample strength signal captured by the configuration;

[0070] Figure 3 A schematic flow chart showing a method according to the invention; and

[0071] Figures 4 to 7 A schematic diagram is shown to further illustrate the functional principle of the invention. DETAILED DESCRIPTION

[0072] Figure 1A schematic meridional section is shown of a microlithographic projection exposure apparatus 1. The projection exposure apparatus 1 comprises in this case an illumination system 10 and a projection system 20, wherein the illumination system 10 is developed with a configuration 100 according to the invention.

[0073] An object field 11 in an object plane or reticle plane 12 is illuminated by means of an illumination system 10. For this purpose, the illumination system 10 comprises an exposure radiation source 13 which, in the exemplary embodiment shown, emits illumination radiation which at least comprises the light used in the EUV range, that is to say in particular has a wavelength between 5 nm and 30 nm. The exposure radiation source 13 can be a plasma source, for example a laser produced plasma (LPP) source or a gas discharge produced plasma (GDPP) source. It can also be a synchrotron-based radiation source. The exposure radiation source 13 can also be a free electron laser (FEL).

[0074] The illumination radiation emitted from the exposure radiation source 13 is initially focused in the concentrator 14. The concentrator 14 may be a concentrator having one or more elliptical and / or hyperbolic reflecting surfaces. The illumination radiation may be incident on at least one reflecting surface of the concentrator 14 at grazing incidence (GI), i.e. at an angle of incidence greater than 45°, or at normal incidence (NI), i.e. at an angle of incidence less than 45°. The concentrator 14 may be structured and / or coated firstly with a view to optimizing its reflectivity for the radiation used and secondly with a view to suppressing extraneous light.

[0075] The illumination radiation propagates through an intermediate focus in an intermediate focal plane 15 downstream of the condenser 14. If the illumination system 10 is constructed in a modular design, the intermediate focal plane 15 can in principle be used to separate (including structurally) the illumination system 10 into a radiation source module (including exposure radiation source 13, condenser 14) and the illumination optical unit 16 described later. In the case of a corresponding separation, the radiation source module and the illumination optical unit 16 then together form the modularly constructed illumination system 10.

[0076] The illumination optical unit 16 comprises a deflection mirror 17. The deflection mirror 17 can be a flat deflection mirror or, alternatively, a mirror having a beam influencing effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 17 can be embodied as a spectral filter which separates the used light wavelength of the illumination radiation from extraneous light whose wavelength deviates therefrom.

[0077] The deflection mirror 17 serves to deflect the radiation emitted by the exposure radiation source 13 to a first facet mirror 18. If, as in the present case, the first facet mirror 18 is arranged in a plane of the illumination optical unit 16 which is optically conjugate to the reticle plane 12 (as a field plane), this facet mirror is also referred to as a field facet mirror.

[0078] The first facet mirror 18 comprises a plurality of micromirrors 18' which can be pivoted individually about two mutually perpendicular axes in each case to controllably form facets, each facet being provided with an orientation sensor (not shown) for determining the orientation of the micromirror 18'. The first facet mirror 18 is therefore a microelectromechanical system (MEMS system), as is also described, for example, in DE 10 2008 009 600 A1.

[0079] The second facet mirror 19 is arranged downstream of the first facet mirror 18 in the beam path of the illumination optical unit 16, as a result of which a two-facet system is produced, the basic principle of which is also referred to as a fly-eye integrator. If, as in the described exemplary embodiment, the second facet mirror 19 is arranged in the pupil plane of the illumination optical unit 16, it is also referred to as a pupil facet mirror. However, the second facet mirror 19 can also be arranged at a distance from the pupil plane of the illumination optical unit 16, as a result of which a specular reflector is produced by the combination of the first facet mirror 18 and the second facet mirror 19, as described in US 2006 / 0132747 A1, EP 1 614 008 B1 and US 6,573,978.

[0080] The second facet mirror 19 is not composed of pivotable micromirrors, but rather comprises individual facets formed by one mirror or a much larger manageable number of mirrors compared to the micromirrors, which facets are either fixed or tiltable only between two defined end positions.

[0081] The individual facets of the first facet mirror 18 are imaged, usually only approximately, into the object field 11 by means of a second facet mirror 19. The second facet mirror 19 can be the last beam-shaping mirror or indeed the last mirror of the illuminating radiation in the beam path upstream of the object field 11.

[0082] In each case, one of the facets of the second facet mirror 19 is assigned to exactly one of the facets of the first facet mirror 18 to form an illumination channel for illuminating the object field 11. This can in particular produce an illumination according to the Kohler principle.

[0083] The facets of the first facet mirror 18 are imaged overlapping each other by the correspondingly assigned facets in the second facet mirror 19 to completely illuminate the object field 11. Here, the entire illumination of the object field 11 is as uniform as possible, preferably with a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0084] By selecting the illumination channel that is ultimately used, which can be done without problems by appropriate setting of the micro-mirrors 18' of the first facet mirror 18, it is still possible to set the intensity distribution in the entrance pupil of the projection system 20 as described below. This intensity distribution is also referred to as the illumination setting. Incidentally, it may be advantageous to arrange the second facet mirror 19 not exactly in a plane that is optically conjugate with the pupil plane of the projection system 20. In particular, the pupil facet mirror 19 can be arranged to be inclined relative to the pupil plane of the projection system 20, as described, for example, in DE 10 2017 220 586 A1.

[0085] However, in Figure 1 In the configuration of components of illumination optical unit 16 shown, pupil facet mirror 19 is arranged in a region conjugate to an entrance pupil of projection system 20. Deflection mirror 17 and the two facet mirrors 18, 19 are arranged in each case tilted relative to object plane 12 and relative to each other.

[0086] In an alternative embodiment (not shown) of the illumination optical unit 16, a transfer optical unit comprising one or more mirrors can be additionally provided in the beam path between the second facet mirror 19 and the object field 11. The transfer optical unit can in particular comprise one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors). Using an additional transfer optical unit, in particular different attitudes of the entrance pupil for the tangential beam path and the sagittal beam path of the projection system 20 as described below can be taken into account.

[0087] Alternatively, you can omit Figure 1 The deflection mirror 17 shown and, for this purpose, the facet mirrors 18 , 19 should be appropriately arranged relative to the radiation source 13 and the concentrator 14 .

[0088] By means of the projection system 20 , the object field 11 in the reticle plane 12 is transferred to an image field 21 in an image plane 22 .

[0089] To this end, the projection system 20 includes a plurality of mirrors M i , which are numbered sequentially according to their configuration in the optical path of the projection exposure apparatus 1 .

[0090] exist Figure 1 In the example shown, the projection system 20 includes six reflectors M1 to M6. Alternatively, there may be four, eight, ten, twelve or any other number of reflectors M1 to M6. i The penultimate mirror M5 and the last mirror M6 both have a passage opening for the illumination radiation, so that the depicted projection system 20 is a double-blocking optical unit. The image-side numerical aperture of the projection system 20 is greater than 0.3, and may also be greater than 0.6, and may be, for example, 0.7 or 0.75.

[0091] Reflector Mi The reflective surface of the reflector M can be specifically implemented as a free-form surface without a rotational symmetry axis. i The reflective surface of the illumination optical unit 16 can also be designed as an aspherical surface having exactly one axis of rotational symmetry of the reflective surface shape. i There may be highly reflective coatings for the illuminating radiation. These coatings may be designed as multilayer coatings, in particular with alternating molybdenum and silicon layers.

[0092] The projection system 20 has a large object-image offset in the y direction between the y coordinate of the center of the object field 11 and the y coordinate of the center of the image field 21. This object-image offset in the y direction may be approximately the same as the z distance between the object plane 12 and the image plane 22.

[0093] In particular, the projection system 20 can be designed to be deformable, that is to say it can have different imaging ratios β in particular in the x-direction and in the y-direction. x , β y The two imaging ratio β of the projection system 20 x , β y Preferably (β x , β y ) = (+ / - -0.25, + / - -0.125). An imaging ratio β of 0.25 corresponds to a reduction of the ratio 4:1, while an imaging ratio β of 0.125 leads to a reduction of the ratio 8:1. A positive sign of the imaging ratio β indicates imaging without image inversion; a negative sign indicates imaging with image inversion.

[0094] Other imaging ratios are also possible. Imaging ratios β with the same sign and the same absolute magnitude in the x and y directions x , β y It is also possible.

[0095] The number of intermediate image planes in the x-direction and the y-direction in the beam path between the object field 11 and the image field 21 may be the same or may be different, depending on the specific embodiment of the projection system 20. Examples of projection systems 20 with different numbers of such intermediate images in the x-direction and the y-direction are known from US 2018 / 0074303 A1.

[0096] In particular, the projection system 20 may comprise a concentric entrance pupil. The latter may be accessible. However, it may also be inaccessible.

[0097] A reticle 30 (also referred to as a mask) arranged in the object field 11 is exposed by the illumination system 10 and transferred by the projection system 20 to the image plane 21. The reticle 30 is held by a reticle carrier 31. The reticle carrier 31 can be displaced, in particular in a scanning direction, by a reticle displacement drive 32. In the exemplary embodiment shown, the scanning direction extends along the y-direction.

[0098] The structures on the reticle 30 are imaged on the photosensitive layer of a wafer 35, wherein the wafer is arranged in the image plane 22 in the region of the image field 21. The wafer 35 is held by a wafer carrier 36. The wafer carrier 36 can be displaced, in particular longitudinally with respect to the y-direction, by a wafer displacement drive 37. The displacement of the reticle 30 firstly by the reticle displacement drive 32 and the displacement of the wafer 35 secondly by the wafer displacement drive 37 can be carried out synchronously with one another.

[0099] Figure 1 The projection exposure apparatus 1 shown or its illumination system 10 is developed using an arrangement 100 according to the invention, the above description of which essentially reflects the known prior art. In this case, the arrangement 100 comprises as structural components a calibration radiation source arrangement 101 and a plurality of calibration radiation sensor arrangements 102.

[0100] In the exemplary embodiment shown, the calibration radiation source device 101 is designed as a radiation source separate from the exposure radiation source 13 and is arranged in the region of an intermediate focus or intermediate focal plane 15 of the exposure radiation source 13. However, the exposure radiation source 13 can also be used as the calibration radiation source device 101. Furthermore, a plurality of calibration radiation source devices 101 can be provided, one of which can be the exposure radiation source 13.

[0101] Figure 1 The calibrated radiation source device 101 shown emits light in the visible light range, wherein the actual light source is arranged outside the illumination system 10 and the light generated thereby is transmitted via Figure 1 Suitable optical fibers are introduced into the lighting system 10 at the locations shown.

[0102] Furthermore, in the exemplary embodiment shown, two calibration radiation sensor devices 102 are provided which are arranged in the vicinity of the reticle plane 12 away from the region provided to the reticle 30. The calibration radiation sensors 102 are arranged on both sides of the scanning direction (extending in the y-direction in the example shown) without interfering with the actual exposure of the reticle 30 and without hindering any displacement of the reticle carrier 31 in the scanning direction.

[0103] Each of calibration radiation sensor devices 102 is an intensity detector designed for the wavelength of the radiation of calibration radiation source device 101 , each intensity detector being formed with an aperture and a narrowband wavelength filter adapted to the radiation of calibration radiation source device 101 .

[0104] A calibration beam path 103, 104 can be defined for each individual pivotable micromirror 18' of the facet mirror 18, some of which are located in the Figure 1 Each calibration beam path 103, 104 is guided from the calibration radiation source device 101 via a specific micromirror 18' of one facet mirror 18 and a predefined facet on another facet mirror 19 to the predefined calibration radiation sensor device 102, wherein the facet of the facet mirror 19 is usually different from the facet that is illuminated by the micromirror 18' for actually exposing the mask 30. Independently, the calibration beam paths 103, 104 (as shown) can also be guided additionally via the deflection mirror 17 and / or any further transfer optical unit (not shown).

[0105] In order to use the arrangement 100 for system-integrated calibration of the facet mirror 18 of the illumination system 10 and thus for carrying out the method 200 according to the invention (see Figure 3 ), specifically systematically pivoting the micromirrors 18' contained in the specific defined calibration beam paths 103, 104, while monitoring the signals of the calibration radiation sensor devices 102 assigned to the respective calibration beam paths 103, 104 (see Figure 3 , step 210).

[0106] In this case, the micromirror 18' is pivoted systematically, in particular at least within the pivoting range in which radiation is incident on the calibration sensor device 102 along the defined calibration beam path 103, 104. For this purpose, assuming a certain basic calibration, the micromirror 18' can be pivoted into an orientation provided for the defined calibration beam path 103, 104, and it can then be generally assumed that the radiation incident on the calibration sensor device 102 is actually deflected by the micromirror 18' in question. Of course, in this case, it is necessary to ensure that no other beam paths from the calibration radiation source device 101 reach the calibration radiation sensor device 102, which can however be achieved, for example, by appropriate pivoting of the remaining micromirrors 18' of the facet mirror constructed therefrom, which is generally possible without any problems even if there is only a basic calibration for the remaining micromirrors 18'. In particular, the remaining micromirrors 18' can also be pivoted appropriately for the actual exposure of the reticle 30. Alternatively, the remaining micromirrors 18' can also be pivoted into respective end positions of their pivot range, in which a beam path from the calibration radiation source device 101 to the calibration radiation sensor device 102 cannot be realized via the micromirror 18' in question. Likewise, if possible, the facets of the further facet mirror 19 which are not associated with the defined calibration beam path 103, 104 can also be tilted into a defined position, in which no radiation from the first facet mirror 18 is deflected in the direction of the calibration radiation sensor device 102.

[0107] In this case, if the calibration radiation sensor device 102 cannot detect radiation, in the exemplary embodiment shown, this may mean that the calibration radiation reflected by the micro-reflector 18' is not incident on any radiation reflecting facet of the other facet mirror 19, or that the radiation deflected by the facet mirror 19 and coming from the micro-reflector 18' is not incident on the calibration radiation sensor device 102 at all.

[0108] If the micro-mirror 18' to be calibrated is pivoted accordingly, the intensity I of the incident radiation determined by the calibration radiation sensor device 102 can be recorded as a function of the orientation α captured by the orientation sensor of the micro-mirror 18' as follows by Figure 2 Let's take an example. In this case, Figure 2 The illustration in is limited to the pivoting about the pivot axis of the micromirror 18' perpendicular to the drawing plane. If, as in the present case, the micromirror 18' can be pivoted about two axes, a particularly systematic pivoting can also be performed on each axis, which can be considered simultaneously or successively with a time offset.

[0109] Based on the data thus recorded, the optimum pivot position of the micromirror 18' for a particularly systematic pivoting can be determined (see Figure 3, step 220), for this optimal pivot position, the calibration beam paths 103, 104 are incident on the calibration radiation sensor 102. In the present example herein, the optimal pivot position corresponds to an intensity I max,med The central maximum value of .

[0110] For the thus determined max、med The optimal pivot position of the micromirror 18 ′ can be determined from the recorded data by determining the orientation α1 of the micromirror 18 ′ which is pivoted in a particularly systematic manner and indicated by the orientation sensor of the micromirror (see Figure 3 , step 230).

[0111] Based on the knowledge of the configuration of the calibration radiation source device 101, the facet mirrors 18, 19 and in particular the micromirror 18' and the calibration radiation sensor device 102, it is also possible to calculate the orientation α* of the particularly systematically pivoted micromirror 18' which should correspond to the optimal pivot position and which should in fact have been indicated by the orientation sensor. By comparing the orientation α1 detected by the orientation sensor for the optimal pivot position with the orientation α* calculated for this pivot position (see Figure 3 , step 240), in principle the calibration of the orientation sensor can already be adjusted for this pivot position based on the comparison (see Figure 2 , step 250).

[0112] However, for a particular micro-mirror 18' to be pivoted in a particularly systematic manner, the above steps 200-240 need to be performed for a plurality of defined calibration beam paths 103, such as Figure 1 As shown in (see Figure 3 , arrow 245). In particular, a total of, for example, five different calibration beam paths 103 may be provided for a micro-reflector 18' that is pivotable about two axes. In this case, the five calibration beam paths 103 are preferably defined such that the orientations adopted by the micro-reflectors 18' to be calibrated do not lie in a common plane.

[0113] This results in a total of five described comparisons of detected and calculated orientations α1 , α* for the respective optimal pivot position of the micromirror 18 ′ to be pivoted, in each case for one beam path 103 (see Figure 3 , step 240), and these can be used to recalibrate the orientation sensor of the micro-reflector 18' (see Figure 3 , step 250).

[0114] This is particularly helpful for orientation sensors that have a possibly non-linear two-dimensional characteristic curve due to pivotability about two separate axes, since the five support points resulting from the five aforementioned comparisons are usually sufficient to adapt the two-dimensional characteristic curve of the orientation sensor over the entire pivot range, thereby enabling a complete recalibration of the orientation sensor. However, depending on the characteristic curve of the orientation sensor or the required calibration accuracy, significantly more calibration beam paths 103, 104 may naturally be required, as well as a comparison of the results to perform a proper calibration.

[0115] In order to be able to define a sufficient number of calibration beam paths 103, 104 for the calibration of each micromirror 18' of the facet mirror 18, it may be necessary to provide more than two calibration radiation sensor devices 102 or additional calibration radiation source devices 101. In particular, in this case, a plurality of calibration radiation sensor devices 102 may be arranged in series on both sides of the reticle carrier 31. However, the calibration radiation sensor device 102 may also be formed as a one-dimensional or two-dimensional array sensor, for example, which is designed in each case for the wavelength from the calibration radiation source device 101 and makes it possible to determine, in addition to the radiation intensity incident on the array sensor, the position of incidence in at least one direction. The position of incidence of the calibration beam paths 103, 104 on the calibration radiation sensor device 102 is then appropriately taken into account during the calibration of the orientation sensor of the micromirror 18'.

[0116] According to an alternative embodiment, at least one calibration radiation sensor device 102 is arranged in the region of the intermediate focus 15 ′ of the exposure radiation source 13 and at least one calibration radiation source device 101 is arranged near the reticle plane 12 , away from the region provided to the reticle 30 .

[0117] The functional principle of the present invention is again Figures 4 to 7 In this case, the long dashed line represents the beam path portion used for actually exposing the reticle 30, while the dotted line is the calibration beam path 103.

[0118] In order to calibrate the orientation sensors of the micromirrors 18' on the field facet mirror 18 (wherein a group of micromirrors 18' can in each case form a (virtual) field facet 18''), the imaging properties of the pupil facets 19" of the further facet mirror 19 are utilized so that in the region of the reticle 30, a calibration beam path 103 passing through the micromirrors 18' from a calibration radiation source device 101 in the region of the intermediate focus 15' is incident on a calibration radiation sensor device 102 arranged in this region in a manner displaced in the scanning direction (see Figure 6). However, the calibration beam path 103 reaches the calibration radiation sensor device 102 only when the micro-mirror 18' to be calibrated is tilted, so that the radiation from the calibration radiation source device 101 actually also impinges on the (virtual) pupil facet 19" which is suitable for the desired calibration beam path 103. In this case, for example a top-hat-like excursion at the calibration radiation sensor device 102 can be determined depending on the tilt angle of the micro-mirror 18' to be calibrated, as Figure 2 As shown in the example.

[0119] In order to meet the requirement for a plurality of such calibration beam paths 103, one (virtual) partial-field facet 18" may be utilized to be assigned to a plurality of (virtual) pupil facets 19". This assignment may be fixed or dynamically variable.

[0120] In this case, it is advantageous if the calibration radiation sensor device 102 has active surfaces both above (in the scanning direction) and below (in the scanning direction) the reticle 30. It can then be freely selected whether the micromirror 18' to be calibrated is calibrated via a (virtual) pupil facet 19" of a virtual (partial) field facet 18" situated above (see Figure 4 ), or via the (virtual) pupil facet 19" of the virtual (partial) field facet 18" located underneath (see Figure 5 ).

[0121] If the resolution of the calibration radiation sensor device 102 allows, a plurality of micromirrors 18' can also be calibrated simultaneously. For this purpose, for example, a plurality of micromirrors 18' can be directed from the vicinity of a single virtual (partial) field facet 18" to a (virtual) pupil facet 19" associated therewith (see Figure 6 ).

[0122] Alternatively, a plurality of micromirrors 18' can also be directed from the vicinity of different virtual (partial) field facets 18' to respectively associated (virtual) pupil facets 19' (see Figure 7 ). In this case, care should be taken to ensure that the images of the micro-mirrors 18 ′ to be calibrated are not too close, since otherwise the signals of the two micro-mirrors 18 ′ might be superimposed on the calibration radiation sensor device 102 .

Claims

1. An arrangement (100) for the system-integrated calibration of a facet mirror (18) of a microlithography illumination system (10), wherein the facet mirror (18) to be calibrated is configured as a microelectromechanical system with a plurality of individually pivotable micromirrors (18'), which has corresponding orientation sensors for determining the orientation of the micromirrors (18') and is arranged fixedly positioned in the beam path of an illumination optical unit (16) of the illumination system (10), such that a beam emitted from an exposure radiation source (13) is deflected by the exposure optical unit (16) onto the reticle plane (12) of the illumination system (10), the exposure optical unit comprising the facet mirror (18) to be calibrated and a further facet mirror (19) without a microelectromechanical system, Features: At least one calibration radiation source device (101) and at least one calibration radiation sensor device (102) are provided, wherein one device (101, 102) is arranged in the vicinity of the reticle plane (12) of the illumination system (10) away from an area provided for the reticle (12) and its exposure, and the other device (102, 101) is arranged such that, knowing a suitable pivot position of the micromirror (18'), at least one calibration beam path (103, 104) is emitted from one of the calibration radiation source (101) or the calibration radiation sensor device via a predefined micromirror (18') of a facet mirror (18) to be calibrated, and a predefined facet of the other facet mirror (19) to the calibration radiation sensor device (102) or one of the calibration radiation sensor devices is definable.

2. The arrangement as claimed in claim 1, Features: The number, configuration and / or construction of the at least one calibration radiation source device (101) and / or the at least one calibration radiation sensor device (102) are selected so as to define at least one, preferably at least three, preferably at least five calibration beam paths (103, 104) for each micro-mirror (18') in the facet mirror (18) constructed thereby.

3. An arrangement as claimed in any one of the preceding claims, Features: One or more devices (101, 102) arranged in the vicinity of the reticle plane (12) are arranged in a planar manner and / or are disposed on opposite sides of an area provided for the reticle (30).

4. An arrangement as claimed in any one of the preceding claims, Features: Another device (102, 101) is arranged near or in the intermediate focal plane (15) of the illumination system.

5. An arrangement as claimed in any one of the preceding claims, Features: At least one calibration radiation sensor device (102) is an intensity detector, a one-dimensional array sensor, or a two-dimensional array sensor.

6. An arrangement as claimed in any one of the preceding claims, Features: The at least one calibration radiation sensor device (102) has a bandpass filter adapted to the wavelength of the at least one calibration radiation source device (101).

7. An arrangement as claimed in any one of the preceding claims, Features: The calibration radiation source device (101) is an exposure radiation source (13) of the illumination system (10), preferably an EUV exposure radiation source or a separate radiation source.

8. An arrangement as claimed in any one of the preceding claims, Features: The calibration radiation source device (101) is designed to emit light in the visible range and / or is preferably fiber-coupled, wherein the calibration radiation source device (101) preferably comprises a high-power light emitting diode or a laser.

9. An arrangement as claimed in any one of the preceding claims, Features: The facet mirror (18) to be calibrated is a field facet mirror for forming one or more virtual light sources on a pupil facet mirror (19) which is arranged downstream of the beam path and has fixed or merely tiltable facets.

10. An arrangement as claimed in any one of the preceding claims, Features: Each of at least a portion of the micro-mirrors (18') of the facet mirror (18) is capable of pivoting about two non-parallel, preferably mutually perpendicular axes.

11. A method for calibrating a faceted mirror (18) constructed of micromirrors (18') in a microlithography illumination system (20) using the arrangement (100) as claimed in any one of the preceding claims, the method comprising the following steps: a) pivoting a micro-mirror (18') of the facet mirror (18) constructed thereby, the micro-mirror being involved in a defined calibration beam path (103, 104) leading from a calibration radiation source device (101) via an illumination optical unit (16) comprising at least two facet mirrors (18, 19) to a calibration radiation sensor device (102), at least over the pivot range, wherein the calibration beam path (103) is incident on the calibration radiation sensor device (102) and is detected by the latter; b) determining an optimal pivot position of the pivotable micromirror (18') by means of the calibration radiation sensor device (102), in which case the calibration beam path (103, 104) is incident on the calibration radiation sensor device (102) as best as possible; c) determining the orientation of the micro-mirror (18') determined by an orientation sensor of the pivoting micro-mirror (18') for the determined optimal pivot position; d) comparing the orientation determined by the orientation sensor of the pivoting micromirror (18') with an orientation calculated from the defined calibration beam path (103, 104); and e) recalibrating the orientation sensor of the micromirror (18') based on the comparison performed.

12. The method according to claim 11, Features: In order to determine the optimal incidence of the calibration beam path (103, 104) when determining the optimal pivot position in step b), the maximum value of the intensity determined during the pivoting of a micro-mirror (18') by the calibration radiation sensor device (102) designed as an intensity detector, the central maximum value of the intensity determined during the pivoting of a micro-mirror (18') by the calibration radiation sensor device (102) designed as an intensity detector, the rising and falling slopes of the intensity determined during the pivoting of a micro-mirror (18') by the calibration radiation sensor device (102) designed as an intensity detector, the centroid of the intensity determined during the pivoting of a micro-mirror (18') by the calibration radiation sensor device (102) designed as an intensity detector, and / or the incidence position of the calibration radiation sensor device (102) designed as a one-dimensional or two-dimensional array sensor.

13. The method according to any one of claims 11 and 12, Features: For each pivot axis of the micro-reflector (18') to be pivoted, steps a) to d) are performed individually, preferably directly successively.

14. The method according to any one of claims 11 to 13, Features: Steps a) to d) are performed for the micromirror (18') to be pivoted in the facet mirror (18) constructed therefrom, with at least three, preferably at least five different calibration beam paths (103, 104).

15. The method according to any one of claims 11 to 14, Features: For recalibration of the orientation sensor, an n-dimensional characteristic curve of the orientation sensor is adapted, wherein n corresponds to the number of axes about which the associated micromirror (18') can pivot.

16. The method according to any one of claims 11 to 15, Features: With the aid of the remaining micromirrors (18') of the facet mirror (18) constructed on the basis of the micromirrors (18'), the calibration of the micromirrors (18') is carried out in parallel with the microlithographic exposure.

17. The method according to any one of claims 11 to 16, Features: At least one calibration radiation source device (101) is one or more radiation sources different from the exposure radiation source (13) of the illumination system (10) and is spectrally and / or temporally decoupled from the exposure of the exposure radiation source (13).

18. The arrangement as claimed in any one of claims 1 to 10, Features: The arrangement comprises a control device designed to carry out the method according to any one of claims 11 to 17 .

19. A computer program product or a set of computer program products comprising program parts designed to perform the method according to any one of claims 11 to 17 when loaded into a computer or a networked computer connected to the configuration according to any one of claims 1 to 10.

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