DE102018216870A1 - Method for manufacturing a lighting system for an EUV system - Google Patents

Abstract

A method for producing a lighting system for an EUV system comprises the following steps: installing mirror modules (FAC1, FAC2, CO) of the lighting system (ILL) at installation positions provided for the mirror modules, in order to set up an illumination beam path that extends from a source position (SP) up to leads to a lighting field to be illuminated (BF); Coupling measuring light into the illuminating beam path at a coupling position in front of a first mirror module (FAC1) of the illuminating beam path; Detecting the measurement light after reflection of the measurement light on each of the mirror modules of the illumination beam path; Determining actual measured values for at least one system measured variable from detected measurement light, the actual measured values representing an actual state of the system measured variable of the lighting system; Determining correction values from the actual measured values; and adjusting at least one mirror module using the correction values for changing the actual state in such a way that when EUV radiation from the EUV radiation source is irradiated, the illuminating radiation in the illuminating field satisfies a predetermined illuminating specification. At least one of the mirror modules (CO) has a mirror surface on which an IR diffraction structure (DS-IR) is attached, which is designed such that at least a portion of the incident radiation from the infrared range is diffracted out of the illuminating beam path. Measuring light with a wavelength λ from the visible spectral range (VIS) is used, the wavelength λ of the measuring light being selected such that higher orders of measuring light diffracted at the IR diffraction structure (DS-IR) are essentially suppressed.

Description

APPLICATION AREA AND PRIOR ART

The invention relates to a method for producing a lighting system for an EUV system according to the preamble of claim 1 and to a lighting system for an EUV system according to the preamble of claim 9. The EUV system can e.g. are a projection exposure system for EUV microlithography or a mask inspection system working with EUV radiation for the inspection of masks (reticles) for EUV microlithography.

Nowadays, predominantly lithographic projection exposure processes are used to produce semiconductor components and other finely structured components, such as masks for photolithography. Here, masks (reticles) or other pattern generation devices are used that carry or form the pattern of a structure to be imaged, for example a line pattern of a layer of a semiconductor component. The pattern is positioned in a projection exposure system between an illumination system and a projection lens in the region of the object plane of the projection lens and illuminated with an illumination radiation formed by the illumination system. The radiation changed by the pattern passes through the projection lens as projection radiation, which images the pattern onto the substrate to be exposed on a reduced scale. The surface of the substrate is arranged in the image plane of the projection objective that is optically conjugated to the object plane. The substrate is usually coated with a radiation-sensitive layer (resist, photoresist).

One of the goals in the development of projection exposure systems is to lithographically produce structures with increasingly smaller dimensions on the substrate, for example in order to achieve higher integration densities in semiconductor components. One approach is to work with shorter wavelengths of electromagnetic radiation. For example, optical systems have been developed that use electromagnetic radiation from the extreme ultraviolet range ( EUV ) use, especially with working wavelengths in the range between 5 nanometers (nm) and 30 nm, especially at 13.5 nm.

An EUV projection exposure system with a lighting system is, for example, from the patent US 7,473,907 B2 known. The lighting system is designed to receive EUV radiation from an EUV radiation source and to form illuminating radiation from at least a portion of the received EUV radiation. The illumination radiation is directed into an illumination field in an exit plane of the illumination system in the exposure mode, the exit plane of the illumination system and the object plane of the projection objective advantageously coinciding. The illuminating radiation is characterized by certain illuminating parameters and strikes the pattern within the illuminating field at a defined position, shape and size at defined angles. The EUV radiation source, which can be a plasma source, for example, is arranged in a source module separate from the lighting system, which generates a secondary radiation source at a source position in an entry plane of the lighting system.

A plurality of mirror modules are arranged in a housing of a lighting system of the type considered here, which are each in the fully assembled state at the installation positions provided for the mirror modules. The mirror modules or reflecting mirror surfaces of the mirror modules define an illumination beam path that leads from the source position to the illumination field.

The DE 10 2016 203 990 A1 describes methods for producing such a lighting system, the production comprising an adjustment. In the method, mirror modules of the lighting system are installed at installation positions provided for the mirror modules in order to build up an illumination beam path that leads from the source position to the illumination field. Measuring light is coupled into the illuminating beam path at a coupling position in front of a first mirror module of the illuminating beam path and, after reflection, is detected by a detector on each of the mirror modules of the illuminating beam path. Actual measured values for at least one system measured variable are determined from the detected measurement light, the actual measured values representing an actual state of the system measured variable of the lighting system. Correction values that are used for adjustment are determined from the actual measured values. Using the correction values, at least one mirror module is adjusted while changing its position in the installation position in degrees of freedom of the rigid body in order to change the actual state in such a way that when EUV radiation from the EUV radiation source is irradiated, the illuminating radiation in the illuminating field satisfies the illuminating specification. Measurement light is preferably extracted from the visible ( VIS ) Spectral range used.

In the DE 10 2012 010 093 A1 describes an EUV lighting system with a facet mirror that has a variety of facets which each have an IR diffraction structure which is designed such that at least a portion of incident radiation from the infrared range is diffracted out of the illuminating beam path. The wavelength of the IR radiation to be removed is, in particular, the wavelength of a laser which is used to generate a plasma in the EUV radiation source.

TASK AND SOLUTION

It is an object of the invention to provide a method for producing a lighting system which allows reliable production of well-adjusted lighting systems of the type mentioned at the outset. Another task is to provide a well-adjusted lighting system.

To achieve this object, the invention provides a method for producing an illumination system with the features of claim 1 and an illumination system with the features of claim 9. Advantageous further developments are specified in the dependent claims. The wording of all claims is incorporated by reference into the content of the description.

In the method, mirror modules of the lighting system are installed at installation positions provided for the mirror modules in order to build up an illumination beam path that leads from the source position to the illumination field. As part of an adjustment, measuring light is coupled into the illuminating beam path at a coupling position in front of a first mirror module of the illuminating beam path and detected on each of the mirror modules of the illuminating beam path after reflection of the measuring light. Actual measured values for at least one system measured variable are determined from the detected measurement light, the actual measured values representing an actual state of the system measured variable of the lighting system. Correction values are determined from the actual measured values. At least one mirror module is adjusted using the correction values for changing the actual state in such a way that when EUV radiation from the EUV radiation source is irradiated, the illuminating radiation in the illuminating field satisfies the illuminating specification. The method can be used in the initial manufacture of the lighting system by the manufacturer as part of an initial adjustment. The wording `` manufacture of a lighting system '' also includes the use during restoration, e.g. after replacing a mirror module, especially at the end user's place of previous use.

From the actual measured values, e.g. Correction values are determined using sensitivities which represent a relationship between the respective system measured variable and a change in the position of at least one mirror module in its installation position. The correction values show how the actual state has to be changed in order to come closer to the target state. Based on the measurement, an adjustment of at least one mirror module while changing the position of the mirror module in its installation position, i.e. in its rigid body degrees of freedom, using the correction values in order to change the (measured) actual state in such a way that when used as intended, when irradiating EUV radiation from the EUV radiation source, the illuminating radiation in the illuminating field satisfies the illuminating specification. For example, the position of the illumination field in the room can be changed so that it matches the position of the object field of the subsequent imaging optics as closely as possible.

The method is used to produce an illumination system in which at least one of the mirror modules has a mirror surface on which an IR diffraction structure is formed, which is designed in such a way that at least a portion of incident radiation from the infrared range (IR radiation) is diffracted out of the illumination beam path becomes. It can thus be achieved that those infrared radiation components which are diffracted out of the illumination beam path cannot or cannot reach the illumination field in the exit plane of the illumination system and in downstream systems. Radiation from the infrared range includes in particular electromagnetic radiation in the wavelength range from 780 nm to 1 mm. IR radiation can e.g. lead to heat-induced disturbances in projection exposure systems (e.g. heating of optical components, resulting imaging errors).

For example, the IR diffraction structure can be designed such that infrared radiation from the infrared range, for example by approximately 10.6 μm, is diffracted out of the illuminating beam path. Radiation with such IR components can e.g. then get into the illumination beam path when a primary EUV light source in the form of an LPP source (plasma generation by laser, laser-produced plasma) is used in which tin is excited to a plasma by means of a carbon dioxide laser operating at a wavelength of 10.6 μm becomes. Other target wavelength ranges are also possible. For example, the diffraction efficiency for IR wavelengths can be optimized by 1 µm, e.g. in cases in which an Nd: YAG laser is used in the EUV radiation source, which emits at 1064 nm.

For the purpose of adjustment, the method uses measuring light with a wavelength λ from the visible spectral range ( VIS ) used. This has proven to be particularly advantageous in terms of handling and the effort involved in the measurements and allows measurements with high measurement accuracy. For the purposes of this application, the visible spectral range includes in particular wavelengths in the range from 380 nm (violet) to 640 nm (red).

According to the claimed invention, the wavelength of the measurement light is selected such that higher orders of measurement light diffracted at the IR diffraction structure are substantially suppressed. In other words, this means that a predominant portion of the measurement light intensity at the IR diffraction structure is diffracted into the 0th order (0th order). The inventors have found that such measuring light does not affect the measurement or does not affect it in a relevant manner. It was thus recognized that even in lighting systems in which at least one mirror surface bears an IR diffraction structure of the type mentioned, precise measurements with wavelengths from the visible wavelength range can be carried out if the correct wavelength (measuring wavelength) is selected.

The IR diffraction structure can be designed such that it has no significant diffractive effect for the EUV radiation used in the operation of the lighting system. This is to be understood in particular to mean that the intensity of the zero diffraction order of the EUV radiation required for the desired imaging by the IR diffraction structure is at most 10%, in particular at most 5%, preferably at most 1% or less, for example at most 0.1 % is reduced.

The inventors have found that, in contrast, the IR diffraction structures can interfere with measurements with measuring light from the visible spectral range. With typical structure dimensions suitable for diffraction of IR radiation, the diffraction angles for visible light can be so small that the ± 1st orders (ie the - 1st and the + 1st diffraction order) in the illumination field are so close to the 0th diffraction order that they still fall into the lighting field. This can disrupt the measurements. For example, the measurements for determining the position of the illumination field can be disturbed.

This disruptive effect can occur when implementing the invention, i.e. when selecting suitable wavelengths for the measurement, be largely or completely avoided by selecting the wavelength of visible light in such a way that higher diffraction orders (first and higher orders) that arise at the IR diffraction structure are largely suppressed. Higher diffraction orders are suppressed in particular if the intensity in higher diffraction orders is at most 10% of the intensity in the zeroth diffraction order, in particular at most 5%. In other words, in the context of this application, higher diffraction orders are considered to be “essentially suppressed” if the intensity in a higher diffraction order is at most 10%, preferably at most 5%, in particular at most 2% of that intensity that is in the 0th diffraction order is present.

An IR diffraction structure can be aperiodic (non-periodic) or periodic or have both aperiodic and periodic components or ranges. The IR diffraction structure is preferably designed as a diffraction grating, that is to say as a periodic structure through a grating depth d and a grating period p can be marked. In the case of a reflective phase grating in the form of a step grating, the grating depth corresponds to the step height. At a grid depth d the wavelength λ of the measuring light is preferably selected such that the grating depth d essentially corresponds to a half-numbered multiple of the wavelength of the measuring light, so that the condition (d / cos (α) = n · λ / 2) is essentially fulfilled. It is α the angle of incidence of the measuring light to the normal when it strikes the IR diffraction structure and n is a positive integer. The wavelength λ of the measurement light is therefore preferably chosen so that the best possible constructive interference results in the measurement light reflected by the diffraction grating.

If one speaks in this application of a “wavelength of the measuring light”, it is not a single wavelength, but rather a spectrally more or less broad wavelength range or a wavelength band of adjacent individual wavelengths.

A particularly good adaptation of the wavelength of the measuring light to the incident situation on the IR diffraction structure is achieved in a further development in that when measuring with a selected wavelength of the measuring light, a spectral bandwidth of the measuring light is less than 2 nm (full half-value width = full width half maximum = FWHM). The measuring light should therefore be sufficiently narrow-banded so that, given the structure of the IR diffraction structure, as large a proportion of the intensity of the measuring light as possible can fall into the zero order of diffraction.

The above-mentioned condition (d / cos (α) = n · λ / 2) is essentially met in particular if the measuring light has a bandwidth of at most 2 nm and the condition for a wavelength within this bandwidth is exactly met. In other words, it must be taken into account that the above-mentioned condition can only be met exactly for one wavelength. It is crucial for this aspect that the higher orders are suppressed even if you are in a sufficiently small area (2nm) around the exact wavelength.

An EUV lighting system is usually designed so that the EUV radiation can be irradiated into the lighting field from different directions during operation. As a rule, it should be possible to provide different lighting settings, that is to say different lighting intensity distributions in a Fourier level of the field level, the so-called pupil level of the lighting system. In lighting systems with a field facet mirror and a pupil facet mirror, different lighting channels are generally provided for the lighting, one lighting channel being a partial beam path that runs from the source position via a field facet and an associated pupil facet and, if appropriate, further mirror surfaces to the lighting field.

Depending on the location of an IR diffraction structure in the illumination beam path, measurement light from different illumination channels may strike the same IR diffraction structure from different angles of incidence. In this case, in order to achieve a sufficiently strong suppression of higher diffraction orders when using measurement light from the visible wavelength range, it can be advantageous if different beam angles of the coupled measurement light are set in the illumination beam path when coupling measurement light, whereby for individual illumination channels or subgroups of illumination channels different wavelengths of the measuring light can be used with similar beam angles. In other words, the different beam angles can be taken into account in the beam path by using different wavelengths of the measurement light for individual lighting channels or subgroups of lighting channels with similar beam angles. For example, for lighting channels whose angle of incidence on the IR diffraction structure is particularly large, measuring light with a longer wavelength can be used than for lighting channels which are incident perpendicularly or almost perpendicularly on the IR diffraction structure.

The inventors have determined that it can be advantageous if, when measuring with different wavelengths of the measurement light, a spectral range of different wavelengths of the measurement light with a bandwidth of at least 20 nm is used, this bandwidth possibly also being up to 30 nm or more. Under these conditions, it can generally be achieved that the desired suppression of the higher diffraction orders of the measuring light can be achieved with sufficient strength for all angles of incidence possible within the lighting system.

There are different ways of providing the measuring light.

In some embodiments, a measuring light source module that can be adjusted continuously or in steps is used to generate the measuring light. The measuring light source module can have a tunable primary measuring light source which is capable of emitting different wavelengths depending on the setting. For example, it can be a tunable laser light source.

It is also possible for the measurement light source module to have a broadband primary measurement light source and a downstream adjustable device for wavelength selection. The measuring light can therefore come from a broadband primary measuring light source, for example one LED or a thermal radiator, are emitted and subjected to a wavelength selection before being coupled into the illuminating beam path in order to obtain the desired measuring wavelength (ie a narrower wavelength range).

In one embodiment, a measurement light source module is provided which has a primary measurement light source in an entry plane, which is connected downstream of a 4f imaging system for imaging the primary measurement light source in a secondary measurement light source in an exit plane conjugated to the entry plane, with a Fourier plane between the entry plane and a tiltable interference filter is arranged at the exit plane. This is located in the parallel or almost parallel beam path between the entrance plane and the exit plane and can be designed such that, depending on the tilt angle, only a narrow-band region from the incoming broadband light is transmitted or transmitted as measuring light. The interference filter can be tilted in order to continuously tune the wavelength in a certain range. The preferably continuously tiltable interference filter can be arranged in an interchangeable holder, so that the interference filter can be exchanged for another interference filter of the same or a different type without dismantling the device. This can be advantageous, for example, if a single interference filter cannot cover the entire required wavelength range of the measurement light. In this case, you can a plurality of interchangeable interference filters can be provided, which can optionally be moved automatically into the beam path of the measuring light source module by means of a turret arrangement or a linear stage.

A measuring light source module can be attached directly to suitable interface structures of the lighting system for coupling the measuring light source module. Other attachment options can be provided if required. According to a further development, the measuring light is directed from an exit plane of the measuring light source module via a, preferably flexible, light guide to the source position. This makes it possible to mount the measuring light source module with its optical and other components at a suitable distance from the lighting system. The exit of the light guide then generally serves as the measurement light source on the lighting system. The term “light guide” here refers in particular to transparent components such as fibers, tubes or rods that can transport light (here: measuring light) over short or long distances. The light guide is achieved by reflection at an interface of the light guide, either by total reflection due to a lower refractive index of the medium surrounding the light guide, or by mirroring the interface. The light guide can have, for example, a glass fiber or a glass fiber bundle.

The aspect of using a light guide for feeding measurement light into the illumination beam path and the spatial separation between measurement light source module and illumination system during the measurement that is possible as a result can also be advantageous for measurements on illumination systems with mirrors without IR diffraction structures. For example, in the DE 10 2016 203 990 A1 Measuring system described have a light guide between the measuring light source module and the coupling point on the lighting system.

In many embodiments, the mirror modules comprise a first mirror module with a first facet mirror at a first installation position and a second mirror module with a second facet mirror at a second installation position of the lighting system. Such a mirror module has a base body functioning as a carrier, on which facet elements with reflecting facets are mounted individually or in groups in accordance with a specific local distribution. If the reflecting facets of the first facet mirror are located at or near a field plane of the lighting system conjugated to the exit plane, the first facet mirror is often also referred to as a “field facet mirror”. Accordingly, the second facet mirror is often also referred to as the “pupil facet mirror” if its reflective facets are located on or near a pupil plane transformed to the exit plane. The two facet mirrors in the lighting system of the EUV system help to homogenize or mix the EUV radiation.

In many method variants, at least three system measurement variables or performance measurement variables are recorded using the measurement system, namely (i) the position of the illumination field at the reticle level or in the exit plane of the illumination system (corresponding to the object level OS the projection lens); (ii) the spatial distribution of measurement light in a pupil plane of the illumination system transformed to the exit plane Fourier, which determines the telecentricity at the reticle level or in the exit plane, and (iii) a light spot placement on pupil facets, ie the position of a measurement light spot on a facet of the second facet mirror. For details, see the DE 10 2016 203 990 A1 referenced, the disclosure content of which is made by reference to the content of this description.

The method can be used in the original manufacture of the lighting system, i.e. in the case of new manufacture (initial assembly), for the first time to adjust the position of the built-in mirror modules so that the lighting system fulfills the lighting specification when fully assembled. A separate measuring machine can be provided for this initial adjustment, which contains all components of the measuring system. These components generally include a measurement light source module, with which measurement light is generated, and a detector module, with which the measurement light is detected after passing through the relevant part of the illuminating beam path (reflection on all mirror modules) and prepared for evaluation. The measuring machine can contain a measuring frame in which the frame of the lighting system can be installed. Using a positioning system, the frame of the lighting system can be brought into the correct position with respect to the measuring light source module and the detector module so that the measurement can be carried out.

However, there are also cases in which a lighting system of an EUV system has been in operation with an end user for some time and an adjustment should be carried out as part of maintenance work. In particular, it may also happen that a mirror module changes its properties so strongly after long-term use under EUV radiation due to optical, thermal and / or mechanical influences that it is expanded and compared to another, nominally identical or similar, but not yet used mirror module should be replaced. This is also possible within the scope of the claimed invention. The wording “manufacture of a lighting system” therefore also includes a restoration, in particular for the end user at the location of the previous use. Possible prerequisites and strategies for exchanging mirror modules are in the DE 10 2016 203 990 A1 described, the disclosure content of which is made by reference to the content of this description.

Figure list

• 1 zeigt optische Komponenten einer EUV-Mikrolithographie-Projektionsbelichtungsanlage gemäß einer Ausführungsform der Erfindung;
• 2 zeigt einige Strahlverläufe in einer Spiegelanordnung mit zwei Facettenspiegeln;
• 3A und 3B zeigen Beispiele für die mögliche Ausbildung von IR-Beugungsstrukturen in Form binärer Phasengitter an einen Viellagen-Spiegel;
• 4 zeigt schematisch Komponenten eines Beleuchtungssystems gemäß einem anderen Ausführungsbeispiel;
• 5 zeigt ein d-λ-Diagramm zum Zusammenhang zwischen der Stufentiefe d eines binären Phasengitters und der Wellenlänge λÄ des Messlichts für verschiedene Einfallswinkel α von Messlicht;
• 6 zeigt Komponenten eines Messlichtquellenmoduls, welches eine stufenlose Einstellung unterschiedlicher Messwellenlängen in Kombination mit einer Einstellung unterschiedlicher Abstrahlwinkel ermöglicht;
• 7 zeigt Komponenten eines Messlichtquellenmoduls mit einem nachgeschalteten Lichtleiter zur Leitung von Messlicht zu einem entfernten Ort.

Further advantages and aspects of the invention result from the claims and from the following description of preferred exemplary embodiments of the invention, which are explained below with reference to the figures.

• 1 shows optical components of an EUV microlithography projection exposure apparatus according to an embodiment of the invention;
• 2nd shows some beam courses in a mirror arrangement with two facet mirrors;
• 3A and 3B show examples of the possible formation of IR diffraction structures in the form of binary phase gratings on a multi-layer mirror;
• 4th schematically shows components of a lighting system according to another embodiment;
• 5 shows a d-λ diagram on the relationship between the depth of the step d of a binary phase grating and the wavelength λÄ of the measuring light for different angles of incidence α of measuring light;
• 6 shows components of a measuring light source module, which enables a continuous setting of different measuring wavelengths in combination with a setting of different beam angles;
• 7 shows components of a measuring light source module with a downstream light guide for guiding measuring light to a remote location.

DETAILED DESCRIPTION OF THE EMBODIMENTS

1 shows exemplary optical components of an EUV microlithography projection exposure system WSC according to an embodiment of the invention. The EUV microlithography projection exposure system is used to expose one in the area of an image plane IS of a projection lens PO arranged radiation-sensitive substrate W with at least one image of one in the area of an object plane OS of the projection lens arranged pattern of a reflective mask, which is alternatively referred to here as a reticle. In the example, the substrate is a wafer made of semiconductor material, which is coated with a light-sensitive resist layer.

To make the description easier to understand, there is a Cartesian system coordinate system SKS indicated, from which the respective positional relationship of the components shown in the figures results. The projection exposure system WSC is of the scanner type. The x-axis runs in the 1 perpendicular to the plane of the drawing. The y-axis runs to the right. The z axis runs down. The object level OS and the image plane IS both run parallel to the xy plane. During operation of the projection exposure system, the mask and the substrate are moved synchronously or simultaneously in the y direction (scanning direction) during a scanning operation and are thereby scanned.

The facility uses the radiation from a primary radiation source RS operated. A lighting system ILL serves to receive the radiation from the primary radiation source and to form illuminating radiation directed at the pattern. The projection lens PO is used to image the pattern on the light-sensitive substrate.

The primary source of radiation RS can include a laser plasma source or a gas discharge source or a synchrotron-based radiation source or a free-electron laser ( FEL ) be. Such radiation sources generate radiation WHEEL in the EUV range, in particular with wavelengths between 5 nm and 15 nm. The lighting system and the projection lens are constructed with components reflective for EUV radiation, so that they can work in this wavelength range.

At the primary radiation source RS In particular, it can be a plasma source in which tin is excited into a plasma using a carbon dioxide laser operating at a wavelength of 10.6 µm, which among other things emits the desired EUV radiation at approximately 13.5 nm with a relatively high intensity.

The primary source of radiation RS is in one of the lighting systems ILL separate source module SM , among other things, a collector COL for collecting the primary EUV radiation. The source module SM generated in exposure mode at a source position SP in an entry level IT of the lighting system ILL a secondary radiation source SLS . The secondary radiation source SLS is the optical interface between the EUV Radiation source or the source module SM and the lighting system ILL .

The lighting system includes a mixing unit MIX and a flat deflecting mirror operated under grazing incidence GM , which is also called a G mirror GM referred to as. The lighting system forms the radiation and thus illuminates an illumination field BF from that in the object plane OS of the projection lens PO or in the vicinity. The shape and size of the lighting field determine the shape and size of the effectively used object field in the object plane OS . In the area of the object level OS the reflective reticle is arranged during operation of the system. The level OS is therefore also referred to as the reticle level.

The mixing unit MIX consists essentially of two faceted mirrors FAC1 , FAC2 . The first faceted mirror FAC1 is arranged in a plane of the lighting system, that to the object plane OS is optically conjugated. It is therefore also called a field facet mirror. The second faceted mirror FAC2 is arranged in a pupil plane of the illumination system, which is optically conjugated to a pupil plane of the projection objective. It is therefore also called the pupil facet mirror.

With the help of the pupil facet mirror FAC2 and the optical assembly downstream in the beam path, which uses the deflecting mirror operated with grazing incidence GM includes the individual reflecting facets (individual mirror) of the first facet mirror FAC1 mapped in the lighting field.

The spatial (local) illumination intensity distribution at the field facet mirror FAC1 determines the local lighting intensity distribution in the lighting field. The spatial (local) illumination intensity distribution on the pupil facet mirror FAC2 determines the illumination angle intensity distribution in the illumination field OF .

The shape of the illumination field is essentially determined by the shape of the facets of the field facet mirror FAC1 determined, whose images fall into the exit plane of the lighting system. The lighting field can be a rectangular field or a curved field (ring field).

The radiation-guiding area optically between the source position SP and the exit plane (plane of the image field) is the illuminating beam path, in which the EUV radiation in operation successively onto the first facet mirror FAC1 , the second facet mirror FAC2 and the deflecting mirror GM meets.

For further explanation is in 2nd schematically a mirror arrangement SAT shown a first facet mirror FAC1 and a second facet mirror FAC2 having.

The first faceted mirror FAC1 has a variety of first facets F1 on, which are elongated in the embodiment shown arcuate. However, this form of the first facets is only to be understood as an example. Only a few of the facets are shown. The number of first facets is usually much higher in practice and can be over 100 or even over 300.

The second faceted mirror FAC2 has a variety of second facets F2 on, which are designed in the form of small stamps in the embodiment shown, which in turn is only to be understood as an example.

The first facets F1 are on a first base B1 of the first facet mirror FAC1 arranged. The first base body, together with the first facets carried by it and any further components, for example fastening means, actuators, etc., forms a first mirror module SM1 .

The first mirror module SM1 can as a whole on the intended installation position on an associated first support structure TS1 of the lighting system are assembled or removed and removed as a whole. The location of the first mirror module SM1 in space or relative to a reference coordinate system (e.g. the SKS of the housing of the lighting system) by means of the first module coordinate system MKS1 To be defined.

The second facet F2 are in an analogous manner on a second base body B2 of the second facet mirror, creating a completely installable and replaceable second mirror module SM2 is formed. The location of the second mirror module SM2 in space or relative to a reference coordinate system can be done by means of the second module coordinate system MKS2 To be defined.

The relative position or position of a mirror module with respect to the assigned support structures (frame structure of the lighting system) or the associated system coordinate system can be set continuously or incrementally with high accuracy in six degrees of freedom. Suitable adjustment means are provided for this purpose, which can also be referred to as tilting manipulators. Details of possible embodiments are, for example, in the DE 10 2016 203 990 A1 described.

In 2nd are some examples of rays ST drawn in, which illustrate the EUV illumination beam path when the mirror arrangement is installed in an optical system and in operation. The Rays ST go from a first field level here FE1 (Intermediate focus), then from the facets F1 of the first facet mirror FAC1 on the facets F2 of the second facet mirror FAC2 reflected. From the facets F2 of the second facet mirror FAC2 the rays are in a second field level FE2 directed, which corresponds to the exit plane of the lighting system. In the second field level FE2 pictures are created IN THE the facets of the first facet mirror FAC1 , more specifically at the field level FE2 the images of all the first facets F1 superimposed on each other. The overlaid images IN THE together form the illuminated lighting field BF .

Between the facets F1 of the first facet mirror FAC1 and the facets F2 of the second facet mirror FAC2 there is a clear assignment. That means every facet F1 of the first facet mirror FAC1 a certain facet F2 of the second facet mirror FAC2 assigned. In 2nd this is for a facet F1-A and a facet F1-B of the first facet mirror FAC1 and a facet F2-A and a facet F2-B of the second facet mirror FAC2 shown. Those rays ST by the facet F1-A in other words hit the facet exactly F2-A , and those useful light rays that are from the facet F1-B be reflected, meet the facet F2-B , etc. In this case there is a 1: 1 assignment between the facets F1 of the first facet mirror FAC1 and the facets F2 of the second facet mirror FAC2 .

Deviating from a 1: 1 assignment between the facets F1 and F2 However, it is also possible that every facet F1 more than one facet of facets F2 assigned. This is the case when the facets F1 are tiltable, that is to say can assume different tilt positions, so that in a first tilt position each facet F1 a certain facet of the second facets F2 is assigned, and in a different tilt position correspondingly another facet of the second facets F2 . Generally, a 1: n assignment ( n is a natural number) between the first facets F1 and the second facets F2 possible, depending on how many positions the first facets F1 can take.

The illumination beam path is composed of many individual illumination channels, one illumination channel each from the source position or from the intermediate focus FE1 about a first facet F1 and a second facet currently assigned to the first facet F2 leads into the lighting field.

In the exemplary embodiment of the mirror arrangement shown, the first facet mirror is FAC1 to the field level FE2 conjugated and is therefore also called field facet mirror. In contrast is the second facet mirror FAC2 conjugated to a pupil plane and is therefore also referred to as a pupil facet mirror.

The field level FE2 if the mirror arrangement is used in an illumination system of a projection exposure system, the plane in which the reticle, the pattern of which is to be imaged on a wafer, is arranged. In the case of using the mirror arrangement SAT the field level is in a mask inspection system FE2 the plane in which the mask to be inspected is arranged.

In the embodiment of 1 includes the lighting system in addition to a mixing unit MIX acting mirror arrangement with two faceted mirrors FAC1 and FAC2 still the field-shaping mirror operated under grazing incidence GM that is between the second facet mirror FAC2 and the exit plane or the object plane of the projection lens sits. This additional mirror can be inexpensive for reasons of space. In other exemplary embodiments, the lighting system has apart from the two facet mirrors FAC1 and FAC2 no more mirrors in the illumination beam path.

With the lighting system ILL out 1 are all three mirror modules, d .H. the first field facet mirror FAC1 , the second field facet mirror FAC2 and the deflecting mirror GM , interchangeable as a whole. They can therefore be removed from their respective installation positions after loosening the appropriate fastening means and completely replaced, for example with nominally identical components, without completely dismantling the lighting system.

After replacing the mirror, the lighting system should again perform its desired function. In particular, the position of the illumination field in the exit plane should be sufficiently close to its target position and the radiation should again strike the illumination field at a given illumination setting with the same angular distribution as before the mirror replacement. In order to ensure that the optical performance of the lighting system after the replacement of a mirror module systematically corresponds to the desired performance before the mirror replacement, the lighting system provides tools that allow the mirror positions to be changed after installation systematically optimize so that the required optical performance can be achieved in a reasonable time. The devices enable a targeted adjustment of the lighting system at the point of use, for example at the manufacturer of semiconductor chips.

The lighting system is made up of components of a measuring system MES equipped, which allows to obtain optically information for determining the positions of the mirror modules in the respective installation positions belonging to the mirror modules, so that the adjustment can be carried out systematically on the basis of the measured values obtained by the measuring system. The measuring system MES of the exemplary embodiment has the following components.

A measuring light source module MSM contains a measuring light source MLS for emitting measuring light from the visible ( VIS ) Spectral range. For example, a light-emitting diode ( LED ) or a laser diode can be used. The measuring light source module MSM is using the first interface structures IF1 on the housing H the lighting system is arranged outside the evacuable interior, can be mounted for the purpose of measurement and, if necessary, dismantled and, if necessary, used elsewhere for measurement purposes. The position of the measuring light source module in relation to the housing can be changed with the help of positioning drives in multiple axes, both parallel to the central direction of radiation and perpendicular to it. An embodiment of a measuring light source module is in connection with 5 explained in more detail.

A switchable coupling device IN is intended for measuring light which is from the measuring light source module MSM is emitted in the illuminating beam path at a coupling position in front of the first facet mirror FAC1 to couple. The coupling device comprises a coupling mirror MIN serving plane mirror, which can be pivoted with the aid of an electric drive between a neutral position shown in dashed lines outside the illumination beam path and the coupling position shown with a solid line. In the example, the measuring light source module generates at the location of the source position SP (Intermediate focus of EUV radiation) an image of the measurement light source MLS . The coupling mirror MIN can be swiveled so that the measuring light beam at the location of the source position SP is coupled into the illumination beam path as if the measuring light source MLS at the location of the source position SP are located. With this arrangement, the source beam present in EUV mode can thus be imitated or simulated with the aid of measuring light.

Behind the last mirror module of the illumination beam path, in the example from 1 so behind the deflecting mirror GM , is in the area between the deflecting mirror GM and the exit level of the lighting system (object level OS of the projection lens) a switchable decoupling device OUT for coupling out measurement light from the illumination beam path, the measurement light being coupled out after the measurement light has been reflected on each of the mirror modules of the illumination beam path. The switchable decoupling device comprises a decoupling mirror MOUT used plane mirror, which can be pivoted with the help of an electric drive between the neutral position shown in dashed lines outside the illumination beam path and the decoupling position shown with a solid line. In the decoupling position, the decoupling mirror reflects that from the deflecting mirror GM incoming measuring light in the direction of a detector module position, in which a detector module DET is arranged.

The detector module DET is using two interface structures IF2 on the outside of the case H of the lighting system in its detector position and can be adjusted in position using electrically controllable positioning drives. An embodiment of a detector that can be used for this is shown in FIG DE 10 2016 203 990 A1 described. To this extent, the disclosure of this document is incorporated by reference into the content of the description.

All controllable components of the measuring system MES are ready for operation when the measuring system is installed and transmit signals with the control unit SE connected to the measuring system. In the control unit there is also an evaluation unit for evaluating the measurement values obtained using the measurement light, which represent the adjustment state of the mirror modules within the lighting system.

At least one mirror surface of one of the mirror modules is provided with an IR diffraction structure for diffraction of radiation of a wavelength in the infrared range. In the example, the diffraction structure should be suitable for preventing disruptive infrared light, in particular with a wavelength of approximately 10.6 μm, from the illuminating beam path or the useful beam path. The IR diffraction structure can e.g. a binary phase grating can be formed.

Analogous to an example from the DE 10 2012 010 093 A1 can, for example, on each mirror surface of the individual facets of the first facet mirror FAC1 an IR diffraction structure DS-IR be trained, for example in the form of a binary phase grating. In 1 such a lattice-like structure for one of the facets is shown schematically enlarged. The binary phase grating preferably has a grating period p on, which is dimensioned such that IR radiation to be masked, which is directed to a facet of the first facet mirror FAC1 does not fall on the second facet of the second facet mirror assigned to this facet FAC2 falls and is thus bent out of the lighting channel formed by the two facets. The binary phase grating can be a grating period, for example p which have the form of the facets of the second facet mirror FAC2 is adapted that the 1st and -1. Diffraction order of IR radiation of the wavelength to be suppressed are imaged on facets of the second facet mirror, which are adjacent to the facet on which the image of an imaged radiation comes to lie. The pupil facets on which the 1st and -1. Diffraction order of the IR radiation to be masked are preferably aligned, for example by tilting, in such a way that the radiation to be masked is not in the illumination field to be illuminated BF in the object level OS is shown. The radiation to be masked out can be deflected, for example, into a light trap.

The 3A and 3B show two examples of the possible formation of IR diffraction structures DS-IR in the form of a binary phase grating. The figures each show a section through a multilayer structure of an EUV mirror perpendicular to the reflecting mirror surface. The mutually parallel, successive layers of high-refractive and relatively low-refractive material to form the EUV-reflecting multilayer layer (multilayer) can be seen. The macroscopically structured mirror surface has front areas V and rear areas H on, which are aligned parallel to each other and in the direction of their surface normal by a predetermined offset d are offset from each other. The front areas V and the back areas H have an identical width in the direction perpendicular to their surface normal in the example. The width of the front areas V is also called the web width, the width of the rear areas H also as furrow width. At least one such front area and such a rear area are usually provided on a mirror surface. However, a large number of such regions can also be provided, in particular in such a way that a lattice structure with a lattice period is formed by the regions p is formed, the grating period also being referred to as the grating constant or pitch. In particular, it can be a binary diffraction grating.

The grid period p can generally be selected in such a way that electromagnetic radiation with wavelengths above that EUV radiation which is used in the operation of the lighting system is deflected away. In the example in which IR radiation is to be masked out, the grating period can be, for example, in the range from 780 nm to 1 mm, in particular in the micrometer range, for example in the range around 10.6 μm.

As in 3A shown, the transitions between front areas V and rear areas H be steep in steps. It is also possible for the webs and furrows to have oblique flanks instead of vertical ones, as exemplified in FIG 3B shown. For example, this can be preferred for reasons of better manufacturability.

In 4th are schematic components of a lighting system ILL shown according to another embodiment. For reasons of clarity, the same reference numerals are used for structurally and / or functionally the same or similar components as in the exemplary embodiment in FIG 1 .

At the primary radiation source RS For example, it can be a plasma source in which tin is excited to a plasma using a carbon dioxide laser operating at a wavelength of 10.6 µm, which among other things emits the desired EUV radiation at approximately 13.5 nm with high intensity. The radiation is from a collector COL bundled. A suitable collector is from, for example EP 1 225 481 A1 known. After the collector, the EUV radiation propagates through an intermediate focus level IT to the following components of the lighting system ILL . At the intermediate focus level IT is the source position SP . The radiation coming from the source position first propagates to the first facet mirror FAC1 (Field facet mirror) and is illuminated by its illuminated facets in the direction of the facets of the second facet mirror FAC2 reflected. The first field facet mirror FAC1 is arranged in a plane of the lighting system that is to the illumination plane OS is optically conjugated. Since the reticle to be illuminated (the mask) is arranged in this plane, this plane is also referred to as the reticle plane. The pupil facet mirror FAC2 is arranged in a pupil plane of the illumination system, which is optically conjugated to a pupil plane of the downstream projection optics. With the help of the pupil facet mirror FAC2 and a subsequent imaging optics TO become illuminated individual facets of the first facet mirror FAC1 (Field facets) in the lighting field so that they overlap there at least partially.

The transmission optics TO of the example 4th contains only a single optical component in the form of a condenser CO with a generally concave mirror surface on which all individual channels of the illuminating beam path fall. In other exemplary embodiments (for example similar to the lighting system from 1 out DE 10 2012 010 093 A1 ) the imaging optical transmission system can also contain more than one component, for example two or three reflecting components connected in series.

In the example of 4th is the concave mirror surface of the condenser CO with an IR diffraction structure DS-IR designed that acts in such a way that at least a portion of the incident IR radiation is deflected out of the illumination beam path in such a way that it does not enter the illumination field BF reached.

The IR diffraction grating on the condenser CO is designed as a reflective phase grating (step grating) in the example and has a grating depth d from a quarter of the wavelength of the infrared radiation to be suppressed, so that the 0th diffraction order for the wavelength of the IR light is suppressed. The grating period (pitch) is chosen such that the diffraction angle for the first diffraction orders for the wavelength of the IR light is approximately in the order of 10 mrad. This results in the reticle level (object level OS of the (not shown) projection lens) a sufficiently large separation of the higher diffraction orders of the IR light from the illuminating beam path or useful beam path.

The phase grating preferably has a grating depth d or furrow depth, which corresponds to just a quarter of a wavelength of IR radiation to be masked out. The grid depth or furrow depth d is in particular in the range from 2 μm to 3 μm, for example in the range from 2.5 μm to 2.7 μm, preferably about 2.65 μm. The diffraction structure has a grating period p (Pitch p ) of at most 5 mm, in particular at most 3 mm, in particular at most 2 mm, in particular at most 1 mm. A smaller grating period leads to a larger deflection angle for the first diffraction order of the IS radiation. The deflection angle can be, for example, at least 3 mrad, in particular at least 5 mrad.

In 4th symbolizes the central beam converging in the direction of the illumination field EUV the illumination beam path of the EUV radiation (desired in operation). Beams are shown to the left and right, starting from the mirror surface of the collector CO not in the direction of the lighting field BF converge, but outside the lighting field BF into the object level OS fall. These represent the +1. Order ( + 1IR ) and the -1. Order ( -1IR ) the infrared radiation diffracted by the IR diffraction structure.

The schematic intensity diagram immediately above the object level in 4th shows the spatial intensity distribution of IR radiation ( IIR ) in the object level OS with intensity maxima at the point of impact of the first diffraction orders and largely suppressed IR intensity in the area of the illumination field BF .

For the measurement in connection with the geometric adjustment of the lighting system (for the initial adjustment in the original production or for an adjustment to restore the performance, e.g. after changing the mirror), the entire illumination beam path is traversed with visible light, for example with a wavelength of the order of approx 500 nm. The measuring light is through the measuring light source module MSM provided. It can be coupled in, coupled out and detected as in connection with 1 described. Some possible measurement methods are in the DE 10 2016 203 990 A1 described. These can be used here. The disclosure of this document is incorporated by reference into the content of the description.

This measuring light also strikes the IR diffraction structures. These structures have no significant diffractive effect for the EUV light used in productive operation. The diffraction angles of the higher orders are in the range of a few µrad and are therefore practically invisible in the reticle plane. For the light used in the measurement from the visible spectral range, i.e. the measurement light, the diffraction angles are, however, of the order of magnitude of 0.5 mrad, so that the -1 on the reticle level. and the +1. Diffraction order of the measuring light is located approximately 1 mm from the zeroth diffraction order. It has been shown that this can interfere with the measurements carried out using the measuring system. In particular, the position measurement of the field position and the measurement of pupil spots can be impaired.

In order to remedy this, the wavelength of the visible light is essentially chosen so that that at the IR diffraction structure DS-IR resulting higher diffraction orders are largely or completely suppressed. If the measurement light is incident perpendicularly on a diffraction grating, this condition is met if the grating depth d just a half number multiple of the wavelength λ corresponds to the measurement light, i.e. d = n · λ / 2. In the event of oblique incidence of the measurement light on a diffraction grating with an angle of incidence α for the surface normal, d / cos (α) = n · λ / 2 with n = 1, 2, 3 ... ..

The schematic intensity diagram immediately above the diagram IIR (x) in 4th shows the spatial intensity distribution of the measurement light from the visible spectral range ( IVIS ) in the object level OS . The majority of the intensity can be found in the 0th diffraction order within the illumination field, higher orders are largely suppressed.

In the lighting system of the type shown here, the different lighting channels (individual channels of the beam path from the source position via a field facet and a pupil facet and possibly one or more mirror surfaces from the transmission optics to the lighting field) have different angles of incidence on the IR diffraction structure. For a sufficiently strong suppression of the higher orders in measurements with visible light, it may be advantageous to select or set the wavelength for the measurement separately for each lighting channel or for groups of lighting channels with relatively similar angles of incidence.

For an exemplary illustration of quantitative relationships shows 5 ad λ diagram on the relationship between the depth of the step d of a binary phase grating, which is designed to suppress 10.6 μ radiation, and the wavelength λ of the measuring light for different angles of incidence α (α = 0, α = 10 °, α = 20 °) of measuring light from the VIS range between 450 nm and 600 nm. It can be seen that measuring light with a tendency to be longer wavelength should be selected if the measuring light is used under relatively larger ( mean) angles of incidence on the IR diffraction structure falls.

For the channel-dependent setting of suitable angles of incidence, the measurement system used to generate the measurement light can have a measurement light source module which can be steplessly or tuned in stages, so that the measurement light source module can generate different required wavelengths of measurement light and which also allows different beam angles with suitable wavelengths to combine. In connection with 6 an embodiment is explained.

It has proven itself in many cases to use a light-emitting diode for system measurement technology with visible light ( LED ) to be used as the primary light source. Taking into account typical incidence angle spectra in the lighting system and the relationships described above between the grating dimensions of a grating that diffracts for IR radiation and the wavelengths of the visible wavelength range used for the measurement, it follows that the wavelength range that is required to achieve the desired suppression for all possible angles of incidence of the higher diffraction orders is about 20 nm to 30 nm wide. Expediently, the measuring light with a bandwidth Δλ <2 nm should also be sufficiently narrow-banded in order to be able to suppress as large a proportion of the measuring light as possible with the higher diffraction orders if the wavelength is set correctly.

The 6 shows components of a measuring light source module MSM , which can meet these parameters. A primary radiation source that is sufficiently broadband in the required wavelength range is thereby used MLS used, for example a light emitting diode ( LED ) or a thermal heater. This primary radiation source is first created using a first Fourier lens FL1 mapped to infinity to create parallel rays. The distance of the first Fourier lens corresponds to this FL1 to the light source just the lens focal length. In the parallel beam path behind the first Fourier lens there is a rotatably mounted, sufficiently narrow-band transmitting interference filter IF . This can be designed, for example, as a dielectric mirror or the like. About the tilt angle β of the filter (measured for example between the optical axis OA of the structure and the surface normal of the interference filter), the transmitted wavelength or the spectral position of a narrow transmitted wavelength range can be set within certain limits. A second Fourier lens FL2 forms the primary light source in an exit plane optically conjugate to the plane of the primary light source AE from. In the back focal plane of the second Fourier lens FL2 this creates an image of the primary light source or a secondary light source SMLS only with the transmitted wavelengths. If the entire required wavelength range cannot be achieved via a single interference filter, several interchangeable interference filters can be provided if required, which can be moved manually or optionally automatically (for example via a turret arrangement or a linear stage) into the beam path.

The measuring light source module is also designed so that different beam angles of the emitted measuring light can be emitted. If necessary, a specific wavelength of the measurement light can be set for each beam angle or a group of similar beam angles. This functionality can be referred to as channel-dependent wavelength adaptation. Between the entrance level, in which the measuring light source MLS located, and exit level AE lies a pupil plane PE , which is a Fourier-transformed plane to the entry plane and exit plane. There is an aperture in the area of the pupil plane CS with an aperture MO through which a selected portion of the measuring light can pass. The position of the aperture MO can be freely selected in two dimensions within the pupil plane. With the help of the sliding cover CS a certain proportion of the measuring light can thus be selected for radiation. The location of the passage opening in the pupil plane determines the angle of incidence of the transmitted measurement light (dashed line) at the location of the secondary measurement light source SMLS and thus also the angle of radiation of the measuring light from the measuring light source module. In this way, different individual channels or channel groups of the lighting system can be selected for a measurement.

The arrangement can be made so that the image of the primary measuring light source MLS , the secondary measuring light source SMLS at the source position SP in the entry level IS of the lighting system is created.

Other constellations are also possible. As in 7 shown, it is possible, for example, the measuring light after the second Fourier lens FL2 to couple into an optical fiber or an optical fiber bundle or another light guide LL and at the source position SP disconnect again. In this case, the entire optical structure of the measurement light source module MSM spatially separated from the lighting system ILL can be arranged and only the light exit of the light guide serves as an effective light source on the lighting system. This can be useful, for example, for a measurement in the field (with a lighting system installed in the projection exposure system at the point of use by the end customer), for example when replacing a mirror. Here a simple channel selection (selection of the angle of incidence) is similar 6 not possible because the measuring light passes through a glass fiber and the entire radiation angle range of the fiber is illuminated again.

In principle, a tunable laser (for example an external cavity diode laser) can also be used as the light source. When using a laser as a light source, there should be additional elements for destroying the coherence and for adapting the optical properties to the input parameters of the lighting system, for example a rotating diffusing screen for destroying the coherence.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 7473907 B2 [0004]
• DE 102016203990 A1 [0006, 0031, 0033, 0035, 0055, 0069, 0084]
• DE 102012010093 A1 [0007, 0072, 0078]
• EP 1225481 A1 [0077]

Claims (14)

Method for producing a lighting system for an EUV system, the lighting system being designed to receive EUV radiation (LR) from an EUV radiation source (LS) at a source position in an entry level and from at least a portion during operation of the EUV system to form the received EUV radiation into illuminating radiation which is directed into an illuminating field in an exit plane (ES) of the illuminating system and which satisfies an illuminating specification in the illuminating field, with the following steps: installing mirror modules of the illuminating system at installation positions provided for the mirror modules for establishing an illuminating beam path, which leads from the source position to the illumination field, coupling measurement light into the illumination beam path at a coupling position in front of a first mirror module of the illumination beam path; Detecting the measurement light after reflection of the measurement light at each of the mirror modules of the illumination beam path; Determining actual measured values for at least one system measured variable from detected measurement light, the actual measured values representing an actual state of the system measured variable of the lighting system; Determining correction values from the actual measured values; Adjusting at least one mirror module using the correction values for changing the actual state in such a way that when EUV radiation from the EUV radiation source is irradiated, the illuminating radiation in the illuminating field satisfies the lighting specification, characterized in that at least one of the mirror modules has a mirror surface an IR diffraction structure is attached, which is designed such that at least a portion of incident radiation from the infrared range is diffracted out of the illuminating beam path; and measurement light with a wavelength λ from the visible spectral range (VIS) is used, the wavelength λ of the measurement light being selected such that higher orders of measurement light diffracted at the IR diffraction structure are substantially suppressed. Procedure according to Claim 1 , characterized in that the IR diffraction structure has a diffraction grating with a grating depth d and that the wavelength λ of the measuring light is selected such that the grating depth essentially corresponds to a half-fold multiple of the wavelength of the measuring light, so that the condition (d / cos ( α) = d = n · λ / 2) is essentially satisfied, where α is the angle of incidence of the measuring light when it hits the IR diffraction structure and n is an integer. Procedure according to Claim 1 or 2nd , characterized in that when measuring with a selected wavelength of the measuring light, a spectral bandwidth of the measuring light is less than 2 nm. Method according to one of the preceding claims, characterized in that when coupling measuring light different beam angles of the coupled measuring light are set in the illuminating beam path, different wavelengths of the measuring light being used for individual illuminating channels or subgroups of two or more illuminating channels with similar beam angles. Method according to one of the preceding claims, characterized in that when measuring with different wavelengths of the measuring light, a spectral range of the measuring light with a bandwidth of at least 20 nm is used. Method according to one of the preceding claims, characterized in that a measuring light source module which can be steplessly tuned or stepped is used to generate the measuring light. Procedure according to Claim 6 , characterized in that the measuring light source module has a tunable primary measuring light source, in particular a laser light source, or in that the measuring light source module has a broadband primary measuring light source and a downstream adjustable device for wavelength selection. Procedure according to Claim 6 or 7 , characterized in that measurement light is guided from an exit plane of the measurement light source module via a, preferably flexible, light guide to the source position. Lighting system for an EUV system, the lighting system being designed to receive EUV radiation (LR) from an EUV radiation source (LS) at a source position in an entry level during operation of the EUV system and from at least a portion of the received EUV Radiation To form illuminating radiation that is directed into an illuminating field in an exit plane (ES) of the illuminating system and that satisfies an illuminating specification in the illuminating field with: a plurality of mirror modules (SM1, SM2, GM) that are installed in the installation positions of the illuminating system provided for the mirror modules and define an illumination beam path from leads from the source position (SP) to the illumination field (BF), at least one of the mirror modules having a mirror surface on which an IR diffraction structure is attached, which is designed such that at least a portion of incident radiation from the infrared range is diffracted out of the illumination beam path ; characterized by integrated components of a measuring system (MES) for measuring measured values, which contain information for determining positions of the mirror modules (SM1, SM2) in the respective installation positions belonging to the mirror modules, the measuring system being configured to measure light at a coupling position in front of a To couple the first mirror module (SM1) of the illuminating beam path into the illuminating beam path and to detect the illuminating beam path after reflection of the measurement light at each of the mirror modules (SM1, SM2, FFM). Lighting system after Claim 9 , characterized in that the measuring system has a measuring light source module (MSM) which can be steplessly or stepped through in order to generate measuring light with a wavelength from the visible spectral range (VIS). Lighting system after Claim 10 , characterized in that the measurement light source module (MSM) has a primary measurement light source (MLS) in an entry plane (E1) and the primary measurement light source has a 4f imaging system for imaging the primary measurement light source in a secondary measurement light source (SMLS) in an exit plane conjugated to the entry plane ( E2) is connected downstream, a tiltable interference filter (IF) being arranged in a Fourier plane between the entry plane and the exit plane. Lighting system after Claim 10 or 11 , characterized in that the measuring light source module (MSM) is configured such that different beam angles of the measuring light can be set in the illuminating beam path, different wavelengths of the measuring light being adjustable for individual lighting channels or subgroups of two or more lighting channels with similar beam angles. Lighting system after Claim 10 , 11 or 12th , wherein the measuring light source module (MSM) has a primary measuring light source (MLS) in an entry plane (E1) and the primary measuring light source is followed by a 4f imaging system for imaging the primary measuring light source in a secondary measuring light source (SMLS) in an exit plane (E2) conjugated to the entry plane is arranged in a Fourier plane between the entry plane and the exit plane a diaphragm (CS) which can be moved transversely to the optical axis of the imaging system and has a passage opening (MO) for measuring light. Lighting system according to one of the Claims 9 to 13 , wherein the measuring system (MES) for performing the method according to one of the Claims 1 to 8th is configured.

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