JP2014003290A - Optical method for measuring angular position of facet of at least one facet mirror for euv use, and optical measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical method for performing high accuracy measurement and setting of the angular position of a facet mirror for EUV use, and to provide an optical measurement device.SOLUTION: In the optical method for measuring the angular position of facets 16, 18 of at least one facet mirror 12, 14 in an optical system designed for EUV use, and then adjusting the angular position depending on the angular position thus measured, the facets 16, 18 of the facet mirrors 12, 14 are illuminated with measuring light, and the measuring light reflected on the facets 16, 18 is detected and evaluated for the purpose of registering the actual angular position. Thereafter, the angular position is adjusted if the actual angular position is deviated from a desired angular position. The optical method is designed so as to register the actual angular position of the facets 16, 18 by an angular position spectrum of at least ±10° with respect to the reference axis.

Description

  The present invention is an optical method for measuring the angular position of a facet of at least one facet mirror of an optical system designed for EUV applications and then adjusting the angular position according to the measured angular position. The facet is illuminated with measurement light, the measurement light reflected from the facet is detected and evaluated to register the actual angular position, and then the actual angular position deviates from the desired angular position The present invention relates to an optical method for adjusting the angular position.

  The invention further provides an optical measuring device for measuring the angular position of the facet of at least one facet mirror of an optical system designed for EUV applications, comprising a measurement light source for illuminating the facet of the facet mirror with measurement light, and a facet The present invention relates to an optical measurement device including a detector that detects reflected measurement light and an evaluation unit that evaluates the detected measurement light to register the actual angular position of the facet.

  An optical method and an optical measuring device of the type mentioned at the beginning are known from US Pat.

  The above document describes a projection exposure apparatus for EUV lithography used for the production of microstructured electronic components. A projection exposure apparatus is used to direct electromagnetic radiation generated by a radiation source to a reticle having a fine structure. The reticle is placed on the object plane of the projection lens of the projection exposure apparatus, and the reticle structure is imaged onto the wafer by the projection lens. This wafer usually contains a semiconductor material and is placed on the image plane of the projection lens. In this case, the wafer is coated with a radiation-sensitive photoresist, and developed after being irradiated with radiation according to the structure of the reticle.

  A projection exposure apparatus for EUV lithography operates with radiation having an extremely short wavelength, precisely with extreme ultraviolet radiation, or EUV radiation for short, the wavelength of which ranges, for example, from about 1 nm to about 50 nm. One exemplary wavelength is 13 nm.

  Since the materials available for the production of refractive optical components such as lens elements are opaque to EUV radiation, the EUV projection exposure apparatus is at least mostly composed of mirrors.

  The facet mirror is accommodated in the illumination system of a known projection exposure apparatus, i.e. between the radiation source and the projection lens. A facet mirror is a mirror having a reflective surface formed from a plurality of individual mirrors referred to herein as facets.

  In this respect, it should be noted that the facet mirror in the present invention can be used not only in the illumination system of the projection exposure apparatus but also in an optical system for other EUV applications.

  The illumination system of the known projection exposure apparatus has two facet mirrors, more precisely the first facet mirror, which is arranged in the field plane and hence also called the field mirror, and the pupil plane of the illumination system, hence the pupil mirror. And a second facet mirror.

  Two facet mirrors, namely a field mirror and a pupil mirror, are used in the illumination system of a projection exposure apparatus to homogenize or mix EUV radiation. In the case of a projection exposure apparatus that operates with a refractive optical element, a fly-eye condenser arrangement having one or more cylindrical lens element arrays usually corresponds to a facet mirror.

  In the case of facet mirrors for EUV applications, the exact angular position of the individual facets of each facet mirror is important for beam shaping quality. At this time, it should be taken into account that the individual facets of the individual facet mirrors can have different angular positions with respect to each other, so that each angular position of each facet is for the proper functioning of the facet mirror in the optical system. It must be adjusted accurately.

  It is therefore necessary to adjust the angular position of the facet to the correct position during the manufacture of the facet mirror, which presupposes a precise measurement of the corresponding angular position of the individual facets.

  In one development of the facet mirror, the individual facets can be tilted so that, for example, different illumination settings can be set during operation of the projection exposure apparatus by tilting the individual or all facets. This is likewise described in the literature cited at the outset, which also discloses a measuring device for allowing the angular position of the tiltable facet to be measured during operation of the projection exposure lens. For this purpose, the known measuring device has a measuring light source and a detector for each facet mirror, and the detector is embodied as a Shack-Hartmann sensor. In this case, the measurement light source directs the measurement light to at least some of the facets of the facet mirror, and the Shack-Hartmann sensor receives the measurement light reflected from the facets. The Shack-Hartmann sensor converts received measurement light into a focus array on a planar CCD array. From the position of the focal point with respect to the reference data, data that subsequently reproduces the angular position of the facet is obtained.

  A disadvantage with this known measuring device is that if the tilt angle of the individual facets is large, the measuring light can travel beyond the Shack-Hartmann sensor after reflection of the facets. Therefore, it is necessary to place the Shack-Hartmann sensor close to the facet mirror, which is difficult for reasons of available structural space, or a very large Shack-Hartmann sensor needs to be provided further away, This is expensive and requires a large structural space.

  Yet another facet mirror construction used in the illumination system of an EUV projection exposure apparatus is described in US Pat. No. 6,057,089, which describes the manufacture of facet mirrors, in particular the adjustment of facets. It is not described how the angular position of the facet can be measured or monitored.

  Patent Document 3 discloses a facet mirror having a tiltable facet, but does not disclose a measurement method for measuring the angular position of the facet. Still other facet mirrors having tiltable facets are described in Patent Literature 4, Patent Literature 5, and Patent Literature 6.

  The requirements for highly accurate measurement and setting of the angular position of the facet mirror have not been fully considered in the prior art, regardless of whether the facet can or cannot be tilted.

International Publication No. 2010/008993 International Publication No. 2008/101656 Specification International Publication No. 2010/079133 International Publication No. 03/040796 Specification US Pat. No. 7,246,909 German Patent No. 102 04 249

  Against this background, the object of the present invention is to develop an optical method and an optical measuring device of the type mentioned at the outset in that highly accurate measurement and setting of the angular position of the facet mirror for EUV applications can be carried out. based on.

  With respect to the optical method mentioned at the outset, this object is achieved by registering the actual angular position of the facets with an angular position spectrum of at least ± 10 ° with respect to the reference axis.

  With respect to the optical measuring device mentioned at the outset, this object is correspondingly achieved by designing the measuring device to register the actual angular position of the facets with an angular position spectrum of at least ± 10 ° with respect to the reference axis. The

  The method according to the invention and the measuring device according to the invention therefore fulfill the requirements for a large measuring range of possible facet angular positions, in which a high-precision measurement of the facets of the facet mirror and the high-accuracy adjustment in connection therewith. to enable. In particular, the method according to the invention and the device according to the invention allow simultaneous measurement of several or all facets of a facet mirror in a single measurement operation. This is because, as already mentioned at the outset, the individual facets of the facet mirror have different angular positions with respect to each other, for example with respect to a reference axis which is the surface normal at the center of the facet mirror body, Because it can span an angular spectrum of at least ± 10 ° with respect to the reference axis. The optical method according to the invention and the optical measuring device according to the invention provide this measuring range with high accuracy. The measurement accuracy is in this case in the range of a few μrad.

  Preferably, in the measuring method according to the invention and the measuring device according to the invention, the actual angular position is registered with an angular position spectrum of at least ± 15 °, more preferably at least ± 20 °.

  In this measurement method, the angular position of the facet can be measured with the facet mirror removed from the optical system, or the angular position of the facet can be measured with the facet mirror incorporated in the optical system.

  Measuring the angular position of the facet with the facet mirror removed from the optical system has the advantage of a simple measuring device configuration, which is correspondingly embodied in this case as an external test bench. Is done. In particular, in this way, facet mirrors of different optical systems can be measured by the same measuring device.

  When measuring the angular position of a facet with a facet mirror built into the optical system, this means that the actual sensitivity of the optical system affects the measurement, and the influence of the entire optical system can be taken into account as well. There are advantages. In particular, it can ensure that the facet mirror shapes the exact beam path of EUV radiation in the optical system by taking into account the interaction of the facet mirrors of the optical system. In order to adjust the angular position of the facets of the facet mirror, the facet mirror is subsequently disassembled and re-assembled into the optical system after adjustment.

  In this case, the measuring device can be appropriately integrated or integrated into the optical system in order to measure the angular position of the facet with the facet mirror incorporated in the optical system.

  In yet another embodiment of the method, a plurality, preferably all, of the facets of the facet mirror are illuminated simultaneously with measurement light, and the measurement light reflected from the plurality, preferably all, of the facets is detected simultaneously. As an alternative, the facets can be illuminated individually and sequentially with measuring light.

  Correspondingly, in the case of a measuring device, the illumination light source simultaneously illuminates several, preferably all, facets of the facet mirror with measuring light, and the detector reflects the measuring light reflected from several, preferably all, facets. Detect at the same time. As an alternative, the measurement light source illuminates the facets individually and sequentially with the measurement light, and both the measurement light source and the detector are movable.

  The simultaneous measurement of the angular position of several or all facets of a facet mirror can be performed with little time, while individual measurements of the angular position of facets can be performed with higher accuracy when appropriate. There are advantages.

  In yet another preferred configuration of the method and the measuring device, the angular position is measured by deflectrometry.

  In this case, it is further preferred to further measure the spatial position of the facet in the direction of the normal to the facet, for this purpose the measuring device further comprises a distance sensor for measuring the spatial position of the facet in the direction of the normal to the facet It is preferable.

  This measure makes it possible to measure not only the angular position of the facet but also the position of the facet in the direction of the beam path of the EUV radiation when the facet mirror is integrated in the optical system.

  The facet mirror in a state incorporated in the optical system is a pupil mirror of the mirror structure, and the mirror structure further includes a field mirror disposed upstream of the pupil mirror, and a field mirror disposed downstream of the field mirror and the field mirror In this method, preferably, the measurement light generated from one point in the plane corresponding to the field plane in a state where the mirror structure is incorporated in the optical system is used as the light beam used during the operation of the mirror structure. The measurement light reflected from the facets of the pupil mirror is captured by the measurement surface along the light beam path that is the same as the opposite direction and the opposite direction, and the orientation and position of the measurement surface is determined by the mirror structure in the optical system. Corresponds to the orientation and position of the field mirror in the assembled state.

  For this purpose, the measurement light source is the same as the light beam path used during the operation of the mirror structure, and the reverse of the measurement light generated from one point in the plane corresponding to the field plane with the mirror structure incorporated in the optical system. It is preferably a point light source that is directed to the pupil mirror along the direction light beam path, and in order to capture the measurement light reflected from the facets of the pupil mirror on the measurement surface, a measurement reticle is arranged, and the orientation and position of the measurement surface Corresponds to the orientation and position of the field mirror with the mirror structure incorporated in the optical system.

  Thus, in this embodiment of the method and measurement device, a partially used beam path of EUV radiation is simulated in the measurement, ie more specifically used in the case of measuring the angular position of the facets of the pupil mirror. Simulate beam path backwards. In this case, the facet of the pupil mirror is illuminated together with the measurement light, and the light reflected from the facet is captured by the measurement reticle so that the captured measurement light can be obtained when the facet of the pupil mirror is at an accurate angular position. Should produce a light spot pattern corresponding to the placement of the center of the facets. However, if this light spot pattern deviates from the (theoretical) position of the field mirror facet center, the facet of the pupil mirror is then moved until the light spot pattern on the measurement reticle corresponds to the center position of the field mirror. adjust.

  Correspondingly, for this purpose, the present measurement method is based on the actual light spot pattern that captures the actual angular position of the pupil mirror as a result of the reflection of the measurement light at the facet of the pupil mirror on the measurement surface. The angle offset of the facet of the pupil mirror is registered by comparing the actual light spot pattern with the desired light spot pattern, and the facet is then adjusted by the angle offset.

  In the measurement device, the detector detects the actual light spot pattern captured as a result of reflection of the measurement light at the facets of the pupil mirror in the measurement reticle, and the evaluation unit responds to the desired light spot pattern. The actual light spot pattern is evaluated in order to register the angle offset of the facets of the pupil mirror.

  In the above embodiment of the present measuring method and measuring apparatus, it is preferable to use light in the visible spectral range as measuring light, and a camera can be used as a detector, and this camera records the actual light spot pattern. In this case, the angular position of the facet is measured with the pupil mirror removed from the optical system, but the measurement structure is the optical element between the downstream field plane and the upstream field mirror that is replaced by a measurement reticle in this procedure. The system is designed to simulate the light beam path used in the system as closely as possible.

  The facet mirror in a state incorporated in the optical system is a field mirror of the mirror structure, the mirror structure further includes a pupil mirror disposed downstream of the field mirror, and the field mirror is disposed upstream of the pupil mirror. If the mirror structure is incorporated in the optical system, the measurement light generated from one point in the plane corresponding to the field plane is the same light beam as the used light beam path during operation of the facet mirror structure. The measurement light reflected from the facet facet of the field mirror is directed along the path and captured by the measurement surface. The orientation and position of the measurement surface is the orientation and position of the pupil mirror with the mirror structure incorporated in the optical system. Corresponding to

  Correspondingly, in the measurement device, the measurement light source uses the measurement light generated from one point in the plane corresponding to the field plane in the state where the mirror structure is incorporated in the optical system as the light used during the operation of the facet mirror structure. A point light source that is directed to the field mirror along the same light beam path as the beam path. In order to capture the measurement light reflected from the facet of the field mirror on the measurement surface, a measurement reticle is arranged, and the orientation and position of the measurement surface Corresponds to the orientation and position of the pupil mirror with the mirror construction incorporated in the optical system.

  As in the case of the measurement of the angular position of the facets of the pupil mirror, in this embodiment of the measurement method and the measuring device, the field mirror is also connected to the optical system during the measurement of the angular position of the facet of the field mirror in the measurement structure. In practice, the actual light beam path is simulated in the forward direction, as opposed to measuring the angular position of the facets of the pupil mirror.

  Here, the actual angular position of the field mirror facet is registered based on the actual light spot pattern captured as a result of the measurement light reflection at the field mirror facet on the measurement surface, and the field mirror facet angle offset Is more preferably registered by comparing the actual light spot pattern with the desired light spot pattern and the facet is then adjusted by the angular offset.

  In the measurement device, the detector detects the actual light spot pattern captured as a result of the reflection of the measurement light at the facet of the field mirror in the measurement reticle, and the evaluation unit detects the desired light spot pattern. The actual light spot pattern is evaluated in order to register the angle offset of the facets of the pupil mirror.

  In yet another embodiment, as an alternative to the above embodiment of the measurement method and measurement device for measuring the facet angular position of the facet mirror based on the principle of simulating the partially used beam path in the forward or reverse direction, The light is directed sequentially as a measurement light beam having a point-like cross section at normal incidence to the center of the facet of the facet mirror, and the measurement light beam reflected from each facet is detected as a light spot, and the actual angular position of each facet Is registered as the deviation of the location of the detected light spot from the reference location.

  The measuring light source of the measuring device correspondingly emits a measuring light beam having a punctiform cross-section and directs it individually and sequentially at substantially normal incidence to the center of the facet of the facet mirror, The measurement light beam reflected from is detected as a light spot, and the evaluation unit registers the actual angular position of each facet as a deviation of the detected light spot location from the reference location.

  In this configuration, as in the previous configuration, the measurement of the angular position of the facet of the facet mirror is performed by deflectometry. At this time, the facets are individually and sequentially scanned by the measurement light. The measuring light is correspondingly directed to a point as a measuring light beam, preferably to the apex of the individual facets, and the reflected measuring light beam is subsequently directed to the detector, for example by a beam splitter, and reflected from the reference position. The beam offset of the measuring light beam is registered and the angle offset of the individual facets is registered therefrom. In this case, the construction comprising the measurement light source and the detector is preferably movable so that all facets can be scanned sequentially.

  The above principle of simulating a partially used beam path has the advantage that facets work during angular position measurement as well as later in operation in the system, but this principle is It is not a prerequisite. This is because the angular position can be obtained even in the measurement beam path deviated from the working beam path.

  In a variation of the above configuration of the method, the angular position of the facet is measured by autocollimation, the measuring light is directed individually and sequentially to the facets of the facet mirror, the measuring light illuminates each facet in an area, The measurement light reflected from each facet is detected as a measurement light point after focusing, and the actual angular position of each facet is registered from the displacement of the measurement light point with respect to the reference point.

  Correspondingly, the measurement device has an auto-collimation optical unit, the measurement light source individually illuminates the facets of the facet mirror individually in a planar shape with the measurement light, and the detector measures the measurement light reflected from each facet. Is detected as the measurement light spot after focusing by the focusing optical unit, and the evaluation unit registers the actual angular position of each facet from the displacement of the detected measurement light spot with respect to the reference point.

  In contrast to the above arrangement of the method and the measuring device, each facet is individually illuminated in a plane instead of scanning the individual facets with a measuring light beam to focus the measuring light on the detector. . Preferably, the measuring device has a diverging lens element in the beam path of the measuring light, and the deviation of the measuring light point on the detector relative to the reference point is the center of the wavefront of the reflected measuring light from the focal point of the diverging lens element. Proportional to displacement.

  In yet another alternative configuration of the method, the measurement light is directed individually and sequentially to the facets, the measurement light originating from one point is first collimated and then focused to each facet at substantially normal incidence and reflected from each facet. The collimated measurement light is collimated again, the collimated reflected measurement light is detected as a disc, and the actual angular position of each facet is registered as the detected disc displacement relative to the reference disc.

  Correspondingly, in the measurement device, the measurement light source is embodied as a point light source that sequentially directs the measurement light to the facets, and the measurement light beam path includes a collimator for collimating the measurement light and a measurement light. There is a focusing optical unit that focuses on the facets at substantially normal incidence, the measurement light reflected from each facet is collimated again by the focusing optical unit, and the detector detects the collimated reflected measurement light as a disk and evaluates it The unit registers the actual angular position of each facet as the detected disc displacement relative to the reference disc.

  In this configuration of the method and the measuring device, the facets are again individually scanned in the form of dots in this case, but the reflected measurement light is not incident on the detector in the form of dots, but the measurement light is accurately transmitted in a parallel beam path. Is directed to the detector in the form of a disc. From the detected disc displacement relative to the reference disc, the angular offset of the facet is subsequently registered and used as the basis for subsequent facet adjustment.

  In one development of the above confirmation of the method, a part of the reflected measurement light is detected by white light or colored light interferometry in order to measure the spatial position of each facet in the direction of the normal to each facet. .

  In the measuring device, for this purpose, the measuring light source preferably has an adjustable distance sensor.

  In the above arrangement of the method and the measuring device, the deflectometry for measuring the angular position is combined with an interferometry that determines the spatial position of each facet. In this case, it is further advantageous that the angular position of the facet can be determined particularly accurately by adjusting the distance sensor using the measured distance change. A white light interferometry layer thickness measuring instrument having an upstream cavity may be used as a distance sensor, or a color distance sensor may be used as a measurement light source.

  Yet another configuration of this method is to measure the angular position of the facet by interferometry instead of deflectometry, direct the measurement light individually to the facet by an interferometer, and use the measurement light reflected from each facet as an interference pattern. It is to detect and register the actual angular position of each facet as the slope of the phase plane relative to the reference phase plane.

  Correspondingly, the measurement device has an interferometer, the measurement light source directs the measurement light individually and sequentially to the facets through the interferometer, and the detector detects the measurement light reflected from each facet as an interference pattern. The evaluation unit registers the actual angular position of each facet as the slope of the phase plane relative to the reference phase plane.

  The measurement by the interferometry is also suitable for high-precision measurement of the angular position of the facet of the facet mirror. The measurement conditions during interference by interferometry are almost the same as those by autocollimation. The difference between interferometry and autocollimation is that the aerial image position is evaluated during autocollimation, while interferometry is used. The wavefront slope is evaluated during measurement. Furthermore, in contrast to the measurement by autocollimation, when measuring by the interferometry method, instead of detecting the measurement light spot displacement relative to the reference point and using it to evaluate the actual angular position, the inclination of the phase plane relative to the reference phase plane is used. evaluate. The slope of the phase plane is a measure of the measured angular position of the facet. When measuring by the interferometry, the facets are scanned in a plane.

  Still another configuration of the present method for performing the measurement of the facet angular position of the facet mirror in the state of being incorporated into an optical system will be described below.

  In this configuration, the facet mirror incorporated in the optical system is a pupil mirror that is a mirror structure, the mirror structure has yet another facet mirror that is a field mirror, and the pupil mirror is a facet of the field mirror. Superimpose on each other and form an image on the field plane, and at least one facet of the pupil mirror is assigned to each facet of the field mirror, and the measuring light is directed to the field mirror and the pupil mirror along the used light beam path of the optical system. The individual facets of the field mirror are selected and the actual angular position of the selected facet of the field mirror and / or the assigned facet of the pupil mirror is the displacement of the image of the selected facet from the desired position of the image in the field plane When registered.

  In a related measurement device, the measurement light source directs the measurement light along the working light beam path of the optical system to the field mirror and pupil mirror, the individual facet of the field mirror is selected, and the camera as a detector is placed on the field surface The camera records the image of the selected facet and the evaluation unit determines the actual angular position of the selected facet of the field mirror and / or the facet assigned to the pupil mirror from the desired position of the image in the field plane. Is registered as the displacement of the image of the selected facet.

  The configuration for measuring the pupil mirror removed from the optical system or the field mirror removed from the optical system by simulating the used light beam path upstream or downstream of the pupil mirror or the field mirror with the measurement light is further described above. In contrast, in the above configuration, both the pupil mirror and the field mirror are incorporated in the optical system, and in the actual system, the angular position of the facet of the pupil mirror and / or the field mirror is arranged downstream of the pupil mirror. Measure by registering the position of the selected facet image of the field mirror in the field plane. This can be done using a camera located at or near the field of view. The selection of the individual facets that record the imaging in the field plane with the camera is performed by covering the remaining facets with a stop, or in the case of tiltable facets, by swinging over other facets of the field mirror be able to.

  In this configuration of the method and measuring device, the actual sensitivity of the entire optical system as well as the actual sensitivity of the environment of the optical system can be taken into account, so that the facet of the facet mirror is required during the operation of the optical system. It enables their particularly precise measurement and particularly precise adjustment so that the paths can be shaped as precisely as possible.

  In this procedure, first, a mirror structure composed of two facet mirrors is attached and pre-adjusted, and then incorporated into the optical system. In the optical system, the angular position of the individual facets and their deviation from the desired angular position are measured. Thereafter, the facet mirror is disassembled again from the optical system, and the facet is readjusted in the adjustment state using the deviation of the angular position from the desired angular position obtained in advance. Thereafter, the mirror structure is incorporated again into the optical system.

  Yet another advantage of this procedure is that it also registers and takes into account the interaction between the field mirror and the pupil mirror during the measurement.

  In a development of this arrangement, the actual angular position of the selected facet of the field mirror and / or the assigned facet of the pupil mirror is further registered as a deviation of the actual illumination of the pupil plane from the desired illumination of the pupil plane. .

  In the measurement device, correspondingly, a further detector in the form of a camera is placed at or near the pupil plane, the camera records the illumination of the pupil plane, and the evaluation unit selects the field mirror. The actual angular position of the facets assigned by the facets and / or pupil mirrors is registered as a deviation of the actual illumination of the pupil plane from the desired illumination of the pupil plane.

  The measurement result of the illumination of the pupil plane is also taken into account in the subsequent adjustment of the facets.

  This procedure advantageously takes into account that inaccurate angular positions of the field mirror and pupil mirror facets appear with respect to their influence on the displacement of the field mirror facet image in the field plane. In this case, an inaccurate angular position of the field mirror facets leads not only to displacement of the image in the field plane, but also to displacement of the illumination area of the pupil, i.e. deviation from telecentricity. From the measurement of the illumination area at the field plane and pupil plane of the individual facet channels, it is possible to derive how the field mirror and pupil mirror facets must be directed relative to each other.

  The method according to the invention according to one or more of the above arrangements, if the facets of at least one facet mirror have at least two discontinuous tilt positions that can tilt the facets, or at least one facet mirror This is also applicable when the facets have a continuous tilt position spectrum and the facets can be continuously tilted within the tilt position spectrum. In these two cases, the angular position of the facet is measured for different possible tilt positions. The measuring device is correspondingly designed to measure the angular position of the facets for different possible tilt positions.

  It is possible to measure the angular position of the facets for different possible tilt positions even when the facet mirror is incorporated in an optical system, without causing the disadvantages of the measuring device known from WO 2010/008993 mentioned at the beginning. The enabling method and the configuration of the measuring device are described below.

  For this purpose, in a preferred configuration of the method, the measuring light is first directed to a first mirror array having a plurality of first mirrors with adjustable angular position, and the measuring light is directed from the mirror array to the facet mirror. And directing the measurement light from the facet mirror to a second mirror array having a plurality of second mirrors with adjustable angular position, the first mirror and the second mirror to compensate for the facet tilt during the angular position measurement. The mirror is tilted according to the facet set tilt position.

  An associated measurement device comprises a first mirror array having a plurality of first mirrors with adjustable angular position, and a second mirror array with a plurality of second mirrors with adjustable angular position, and measuring the angular position A controller is provided for tilting the first mirror and the second mirror according to a set tilt position of the facet to compensate for the tilt of the facet.

  In this configuration of the method and measurement device, the measurement light beam is only displaced slightly in parallel for the setting of different tilted positions of the facets intended to measure the angular position, the advantages of which are the measurement light source and the detection The detector can be placed at a greater distance from the facet mirror being measured, and this large distance from the facet mirror being measured does not require a very large detector as is the case with known measuring devices It is.

  Yet another aspect of the method according to the invention relates to the adjustment and fixing of individual facets after measurement of the angular position. To this end, in one configuration, facets are individually pivotally disposed on the body of the facet mirror, each facet having a shaft that passes through the body and seats a centering sleeve and nut, and a plurality of spring legs. The disc spring is arranged between the centering sleeve and the main body, and for the purpose of adjusting the angular position of each facet, the shaft is pivoted by the disc spring relative to the main body with the nut tightened, and if appropriate, The adjusted angular position is then fixed using a fixing means such as an adhesive.

  The construction of facet mirrors, each facet having a shaft that passes through the body and seats a centering sleeve and nut, is described in principle in WO 2008/101565, but the adjustment of the facet is described in that specification. Not mentioned in. In the case of the above configuration, simple adjustment is possible by displacing the disc spring with the nut tightened, and the disc spring is sufficiently self-fixed by friction against the main body, but this fixing is fixed if appropriate. It can be further improved by means, for example by means of an adhesive.

  According to yet another aspect of the invention, the facet mirror structure is used in an illumination device or mask inspection apparatus for EUV lithography.

  A mask inspection apparatus is described in International Publication No. 2009/118130. This mask inspection apparatus has a microscope having an imaging optical unit. The illumination system for illuminating the mask has no more detailed specifications, but is disclosed in this document as a mirror optical unit. The use of a facet mirror structure, preferably a facet mirror structure starting from the light source and having a field facet mirror and a pupil facet mirror in the illumination optical unit has the advantage of uniform illumination of the mask. In this case, it is preferable that the mask is located on a field surface that forms an image of the facet of the field facet mirror. Yet another advantage of the use of a facet mirror arrangement in an illumination device of a mask inspection apparatus for EUV lithography is that the mask can be illuminated in a large field by the facet mirror arrangement.

  In one preferred configuration of the above use, the facet mirror arrangement comprises a first facet mirror having a plurality of first facets and at least one second facet mirror having a plurality of second facets.

  Preferably, the first facet is embodied as an elongated bow and / or the second facet is embodied in a stamp-shaped fashion.

  More preferably, the first facet mirror is arranged in a plane conjugate to the field plane on which the mask to be inspected is arranged, and at least one second facet mirror is arranged in a plane conjugate to the pupil plane.

  Still other advantages and features will be apparent from the following description and the accompanying drawings.

  Needless to say, the features described above and those to be described hereinafter can be used not only in the indicated combination but also in other combinations or singly without departing from the scope of the present invention.

  Illustrative embodiments of the invention are shown and described in greater detail with reference to the drawings.

1 schematically shows a mirror arrangement with two facet mirrors. One of the two facet mirrors from FIG. 1 is shown alone and the individual facets of the facet mirror are also shown. FIG. 2 shows a basic diagram of an optical method for measuring the angular position of one facet of the two facet mirrors in FIG. 1. Fig. 4 schematically shows an optical measuring device for performing the method in Fig. 3; FIG. 2 shows a basic diagram of an optical method for measuring the angular position of the facet of the other facet mirror in FIG. 1. FIG. 6 shows an optical measurement device for performing the method in FIG. FIG. 6 shows a basic view of an optical method and optical measurement device for measuring the angular position of a facet of a facet mirror according to yet another exemplary embodiment. FIG. 6 shows a basic view of an optical method and optical measurement device for measuring the angular position of a facet of a facet mirror according to yet another exemplary embodiment. FIG. 6 shows a basic view of an optical method and optical measurement device for measuring the angular position of a facet of a facet mirror according to yet another exemplary embodiment. FIG. 6 shows a basic view of an optical method and optical measurement device for measuring the angular position of a facet of a facet mirror according to yet another exemplary embodiment. FIG. 6 shows a basic view of an optical method and optical measurement device for measuring the angular position of a facet of a facet mirror according to yet another exemplary embodiment. FIG. 6 shows a basic view of an optical method and optical measurement device for measuring the angular position of a facet of a facet mirror according to yet another exemplary embodiment. Fig. 2 shows the mirror arrangement in Fig. 1 where the facets of two facet mirrors shape the appropriate beam path. FIG. 13B shows the same mirror arrangement in FIG. 13A where the facet mirror facets now shape the incorrect beam path. 2 shows a flowchart of a method for measuring the angular position of a facet when at least one facet mirror is incorporated in an optical system. The basic diagram of the adjustment step for adjusting the angular position of the facet of the facet mirror is shown as an excerpt. FIG. 16 shows a plan view of the partial view of FIG. 15. Fig. 2 shows a basic view of an optical method for measuring the angular position of a facet, which can take different tilt positions. FIG. 2 shows a basic view of an optical method and an optical measuring device for measuring the angular position of a facet of a facet mirror in which the facets can assume different tilt positions. 2 shows a basic view of the use of the mirror arrangement according to FIG. 1 in a mask inspection facility according to an exemplary first embodiment; FIG. 4 shows a basic view of the use of the mirror arrangement according to FIG. 1 in a mask inspection facility according to yet another exemplary embodiment.

  FIG. 1 initially shows as an example a mirror arrangement 10 having a first facet mirror 12 and a second facet mirror 14. As will be described later, the mirror structure 10 is used in an optical system designed for EUV applications, and this optical system is, for example, an optical system that is an illumination system of a projection exposure apparatus or an illumination system of a mask inspection apparatus. An example of an illumination system of a projection exposure apparatus for EUV lithography is described, for example, in FIG. 1 of WO 2010/079133, and this is referred to for an explanation of the illumination system of the EUV projection exposure apparatus.

  The facet mirror 12 has a plurality of facets 16 embodied in the shape of an elongated arc in the illustrated exemplary embodiment. However, it should be understood that this form of facet 16 is exemplary only. Only some of the facets 16 are shown in FIG. In practice, the number of facets 16 is much greater, and can be greater than 100 or greater than 300.

  The facet mirror 14 has a plurality of facets 18 embodied in the form of small stamps in the exemplary embodiment shown, but this is again to be understood as an example only.

  The facet 16 of the facet mirror 12 is arranged on the main body 17, and the facet 18 of the facet mirror 14 is arranged on the main body 19.

FIG. 1 shows by way of example several used light beams 20 showing the EUV used light beam path when the mirror structure 10 is in operation with the optical system incorporated. The used light beam 20 is reflected from the facet 16 of the facet mirror 12 to the facet 18 of the facet mirror 14 after leaving the first field plane F ₁ (intermediate focal point). Facet 18 facet mirror 14, to direct the use beam 20 to the second field plane _{F 2.} In this case, appear on the image 22 is the second field plane F ₂ facet 16 facet mirror 12, More specifically, if the facets 16 and facets 18 is positioned at the correct position with respect to their angular position, of the total The facet 16 images appear on top of each other on the field plane F ₂ of the facet 16.

  There is a one-to-one assignment between facet 16 of facet mirror 12 and facet 18 of facet mirror 14. That is, a specific facet 18 of facet mirror 14 is assigned to each facet 16 of facet mirror 12. FIG. 1 illustrates this for facet 16 a and facet 16 b of facet mirror 12 and facet 18 a and facet 18 b of facet mirror 14. In other words, the used light beam 20 reflected from the facet 16a hits the facet 18a, the used light beam reflected from the facet 16b hits the facet 18b, and so on. In this case, there is a 1: 1 allocation between facet 16 of facet mirror 12 and facet 18 of facet mirror 14.

  However, it is possible to assign more than one facet of facet 18 to each facet 16, deviating from the 1: 1 assignment between facets 16 and 18. This applies to the fact that the facets 16 can be tilted, i.e. they can take different tilt positions, so that each facet 16 is assigned a first facet of facets 18 in the first tilt position and correspondingly different tilt positions. In this case, different facets of facet 18 are assigned. In general, depending on the number of positions that facet 16 can take, a 1: n assignment (n is a natural number) between facet 16 and facet 18 is possible.

In an exemplary embodiment of the mirror structure 10 shown, the first facet mirror 12 are conjugate with respect to the viewing plane F _2, thus also referred to as field mirrors. On the other hand, the second facet mirror 14 is conjugate to the pupil plane and is therefore also referred to as a pupil mirror.

When using a mirror arrangement 10 in the illumination system of the projection exposure apparatus, the viewing surface F ₂ is a plan to place a reticle having a pattern intended for imaging onto the wafer. When using a mirror arrangement 10 in the mask inspection apparatus, the viewing surface F ₂ is a plan to place the mask to be inspected.

If all of the facets 16 used light beam 20 impinges is formed as an image 22 around the center Z of the view surfaces F ₂ overlap with each other, the facet mirror 12 and 14, the EUV radiation (using light beam 20) Shape the appropriate beam path.

  In order to properly shape the beam path of EUV radiation, it is important that the angular position of facet 16 and / or facet 18 is accurate, that is, facet 16 and facet 18 are oriented to the correct position. In particular, the tolerance of the angular position of the facet 18 of the pupil mirror 14 is very small, but the angular position of the facet 16 must also be within specifications.

  Therefore, it is important to precisely measure the individual angular positions of the facets 16 and the individual angular positions of the facets 18, and secondly to make precise adjustments based on the measurement results.

  FIG. 2 again shows the facet mirror 14 alone.

One difficulty with high-precision measurement of the angular position of the facet 18 of the facet mirror 14 is the same for measuring the angular position of the facet 16 of the facet mirror 12, but the facets 18 and 16 on each body 19 and 17 are Not identical for each facet 18 and each facet 16, the angular position is distributed across facet 16 in an angular position spectrum having a bandwidth 2θ _max of at least ± 10 ° with respect to a reference axis 24, for example normal to the surface of body 17. That is. In the illustrated exemplary embodiment, the angular position spectrum bandwidth 2θ _max of facet mirror 14 is about 13 ° and the angular position spectrum bandwidth 2θ _max of facet mirror 12 is about 16 °. The optical methods and optical measurement devices described below for measuring the angular position of facet 16 of facet mirror 12 and facet 18 of facet mirror 14 have an angular position spectrum of at least ± 10 ° with respect to reference axis 24, more preferably ± 15 °. And correspondingly designed to register the actual angular position of facets 16 and 18 with an angular position spectrum of at least 20 °. The proposed method and measuring device are designed not only to register this relatively large measuring range, but also to obtain high measuring accuracy in this measuring range at the same time.

  Yet another problem of the measuring method and measuring device arises when it is desired to simultaneously measure all the angular positions of facet 16 of facet mirror 12 and / or facet 18 of facet mirror 14. For example, since the diameter of facet mirror 12 is approximately equal to 550 mm and the diameter of facet mirror 14 is approximately equal to 200 mm, all such measurements of facet 16 and / or all of facet 18 take into account the diameter of facet mirrors 12 and 14. The issues that were made are also configured at the same time.

  The measurement must also take into account the radius of curvature of the individual facets 16 and 18, which is approximately equal to 1040 mm for the facet mirror 12 and approximately 1100 mm to 1200 mm for the facet mirror 14.

  In that case, the measurement accuracy of the measurement of the angular position of the facets 16 and 18 is intended to be a few μrad.

  Various exemplary embodiments of optical methods and optical measurement devices for measuring the angular position of facets 16 and 18 that can meet the above requirements are described below.

With reference to FIGS. 3-6, an optical method and optical measurement device for measuring the angular position of facet 16 of facet mirror 12 and facet 18 of facet mirror 14 will be described below. As explained on the basis of the use beam 20, the use beam path of EUV radiation is partially simulated in the reverse direction from the field plane F _{2 in} the case of the facet mirror 14, and in the case of the facet mirror 12. partially from view plane F ₁ in the forward direction it is based on the principle that is simulated.

  FIG. 3 illustrates a method by which the angular position of facet 18 of facet mirror 14 (pupil mirror) can be measured as described above based on the principles described above.

  In order to measure the angular position of facet 18 of facet mirror 14 (pupil mirror), facet mirror 14 used during operation of the optical system is disassembled from the optical system.

Measurement light 28, for example, light in the visible spectral range, is emitted from the point 26 on a plane F ₂ corresponding to the field plane F ₂ according to FIG. 1 with the mirror structure 10 incorporated in the optical system. In this case, the point 26 corresponds to the position of the center Z of the image 22 in FIG. A corresponding measurement light source 27 is shown in FIG. The measurement light 28 is directed to the facet mirror 14 in the opposite direction, that is, in the opposite direction, between the facet mirror 14 and the field plane F ₂ according to the used light beam path in FIG. 1, and the measurement light 28 is faceted on the facet mirror 14. Direct to some or all of 18 at the same time. The measuring light beam 28 diverges between the point 26 and the facet mirror 14 correspondingly. The light reflected from the facet 18 of the facet mirror 14 is captured by the measurement surface 30, and the direction and position of the measurement surface 30 are the same as those of the facet mirror 12 in FIG. 1 when the mirror structure 10 is incorporated in the optical system. Correspond. For this purpose, the measurement reticle 32 is arranged on the measurement surface 30.

  On the measurement surface 30, the actual light spot pattern 34 appears due to the reflection of the measurement light 28 at the facet 18, and this pattern corresponds to the midpoint of the facet 16 of the facet mirror 12 if the angular position of the facet 18 is accurate. It has multiple light spots that should be. Correspondingly, the actual light spot pattern 34 for registering the actual angular position of the facet 18 of the facet mirror 14 is affected by whether or not the actual light spot pattern is deviated from the desired light spot pattern. To evaluate. If the individual actual light spots are offset from the desired light spot position, this means that the individual facets 18 of the facet mirror 14 have an angular offset relative to their desired angular position. Facets 18 having an angular offset from the desired angular position are subsequently adjusted until the actual light spot pattern corresponds as closely as possible to the desired light spot pattern.

  FIG. 4 shows a measuring device 40 that can be used to carry out the measuring method according to FIG. The optical measuring device 40 has a frame 42 in which a measuring light source 27 embodied as a point light source, a facet mirror 14, a measuring reticle 32 and a detector 44 in the form of a camera 46 are held. In this case, the camera 46 is movably held by the frame 42 so that the camera 46 can register the measurement reticle 32 for detecting the actual light spot pattern 34. For this purpose, the camera 46 is arranged on a two-dimensional movable table 48 which is movable relative to the frame 42 in two mutually perpendicular directions, which are exactly parallel to the plane of the measurement reticle 32.

  In addition, an adjustment manipulator system 50 is located under the facet mirror 14 which causes the facet 18 of the facet mirror 14 to be based on the results of an evaluation of the comparison between the actual light spot pattern 34 and the desired light spot pattern. Then, adjustment or correction is performed by the angle offset of the facet 18 thus obtained. The measuring device 40 also has an evaluation unit, not specifically shown, which performs an evaluation of the actual light spot pattern and, if appropriate, controls the adjustment manipulator system based on the evaluation.

  The measurement reticle 32 is separated from the right side of FIG. The measurement reticle 32 has a substrate 52, a white screen printing screen 54, and a chrome layer portion 56 that serves as a reference marker.

  An LED ring light can be placed around the lens of the camera 46 to make the reference marker on the measurement reticle 32 visible in the lens of the camera 46.

  The measurement accuracy of the measurement device 40 or the method according to FIG. 3 includes the topography of the measurement reticle 32, the rigid positions of the facet mirror 14, the measurement reticle 32 and the measurement light source 27, the drawing accuracy of the measurement reticle, and the measurement light source 27. And the clarity of the facet edges of facet 18 of facet mirror 14. The installation position of the facet mirror 14 in the measurement device 40 should correspond as much as possible to the installation position of the optical system using the facet mirror 14 in relation to the measurement light source 27 and the measurement reticle 32.

Subsequently, FIG. 5 shows a method similar to the method according to FIG. 3 for measuring the angular position of the facet 16 of the facet mirror 12, in this way as well, on the principle that the measurement simulates the light beam path used. Based. For this purpose, from 60 points located in the intermediate focus F ₁ corresponds in Fig. 1, for example, the measurement light 62 in the visible spectral region is directed to the facet mirror 12 (field mirror), in this case, the measurement light 62, Fig. 1 1 is directed to the facet 16 of the facet mirror 12 corresponding to the used light beam path (used light beam 20) in FIG. 1, and reflected from the facet mirror 12 corresponding to the used light beam path in FIG. The position and orientation of the measurement surface 64 captured by the measurement surface 64 of the reticle 66 correspond to the position and orientation of the facet mirror 14 when the mirror structure 10 is incorporated in the optical system.

  An actual light spot pattern 65 is captured by the measurement surface 64, and the pattern appears as a result of reflection of the measurement light 32 by the facet 16 of the facet mirror 12 on the measurement reticle 66 arranged on the measurement surface 64, and from a desired angular position. In order to register the angle offset of the facet 16, the pattern is appropriately compared with a desired light spot pattern, and the facet 16 is then adjusted by the angle offset.

  FIG. 6 shows a device 70 for measuring the angular position of the facets of the facet mirror 12 in order to carry out the method according to FIG. The measuring device 70 has a frame 72, in which a measuring light source 74, a facet mirror 12, a measuring reticle 66 and a detector 76 in the form of a camera 78 are held. The measurement device 70 further includes a spotlight, such as an LED spotlight 80, for making the reference marker on the measurement reticle 66 visible.

  The measurement reticle 66 is implemented like the measurement reticle 32 in FIG.

  The factor that determines the measurement accuracy of the measurement device 70 is the same as or at least the same as the factor that determines the measurement accuracy of the measurement device 40.

  The measuring method and measuring device described above with reference to FIGS. 3 to 6 operate using deflectometry.

  Yet another refractometry method for measuring the facet angular position of the facet mirror is described below, which is the measurement method and measurement according to FIGS. 3 to 6 in that the facets of the facet mirror are individually measured sequentially. It is different from the device.

  FIG. 7 schematically shows a measuring device 90 for measuring the angular position of the facet 18 of the facet mirror 14 in FIG. 1, and only one individual facet 18 of the facet mirror 14 is shown in FIG. Needless to say, the facet 16 of the facet mirror 12 can also be measured by the measuring device 90. The measuring device 90 has a measuring light source 92, a beam splitter 94, a detector 96 and an evaluation unit 98 with a monitor 100, for example. The measurement light source 92 generates a measurement light beam 102 having a pointed cross-section and directs it at approximately normal incidence to the approximate center of the facet 18. The measurement light beam 102 defines a measurement direction k, and directions w and v perpendicular to the measurement direction k are also indicated by arrows in FIG. Arrow n points in the direction of the normal to facet 18.

  When the angular position of the facet 18, that is, the direction n of the perpendicular line is inclined with respect to the measurement direction k, the measurement light beam 102 is not reflected back when reflected at the facet 18, but the reflected measurement light beam 102 ′ is measured. Reflects at an angle β with respect to the direction k. The reflected measurement light beam 102 ′ is reflected to the detector 96 by the beam splitter 94. Precisely, the measurement light beam 102 ′ strikes the detector 96 as a light spot 104. The light spot 106 refers to a light spot that appears at the detector 96 when the normal direction n to the facet 18 is not tilted with respect to the measurement direction k, that is, when β = 0 ° is true. Accordingly, the angular position of facet 18 is obtained from the light spot displacement of light spot 104 relative to the reference location of light spot 106, and this light spot displacement is displayed on monitor 100. The actual angular position of the facet 18 is registered as a deviation of the detected location of the light spot 104 from the reference location of the light spot 106. The facet 18 is then adjusted to the desired angular position according to the measured angular offset.

  Needless to say, the angular offset of facet 18 is registered spatially. That is, the angle offset components in the spatial directions w and v are also registered.

  FIG. 8 shows yet another exemplary embodiment of a refractometry method and measuring device 110 for measuring the angular position of the facets of a facet mirror, such as the previous exemplary embodiment according to FIG. The facet 18 of the mirror 14 (or similarly the facet 16 of the facet mirror 12) is measured individually and sequentially. Like the measuring method and measuring device 90 according to FIG. 7, the measuring method and measuring device 110 according to FIG. 8 is based on the principle of beam deflection, and specifically the measuring method and measuring device 110 according to FIG. 8 is based on the principle of autocollimation. based on.

  The measuring device 110 has an autocollimation telescope having a diverging lens element 114 and a converging lens 116. The measuring device 110 further comprises an evaluation unit 120 with a detector 118 and a monitor 122. Arrow k indicates the measurement direction, and arrows w and v indicate the spatial direction perpendicular thereto.

  In contrast to the exemplary embodiment in FIG. 7, the measurement light 124 from a measurement light source (not shown) belonging to the autocollimation telescope 112 is directed to the facet 18 in a plane, more precisely in the measurement direction k. The measurement light reflected from the facet 18 is indicated by 124 ', and its principal ray direction is indicated by an arrow h.

M ₀ indicates the virtual focal point of the diverging lens element 114, and M indicates the center of the wavefront of the reflected measurement light 124 ′. The reflected measurement light 124 ′ is focused on the detector 118 via the beam splitter 126 and the converging lens element 116. Accordingly, the converging lens element 116 serves as a converging optical unit. The reflected measurement light 124 ′ generates a measurement light spot 128 at the detector, which deviates from the reference point 129 when the facet 18 is tilted with respect to the measurement direction k, ie is displaced relative to the reference point 129. .

The actual angular position of the facet 18 is registered by the evaluation unit 120 as the displacement of the measurement light spot 128 relative to the reference point 129, and the displacement of the measurement light spot 128 is reflected measurement light 124 ′ with respect to the virtual focus M ₀ of the diverging lens element 114. Is proportional to the displacement of the spatial position of the center M of the wavefront.

  Therefore, in this procedure, the angular position of the facet of the facet mirror is measured as an offset of the center of curvature of the facet.

  FIG. 9 shows yet another exemplary embodiment of a method for measuring the facet angular position of a facet mirror by means of a measuring device 130, which is based on the principle of retroreflection.

  The measuring device 130 comprises a measuring light source 132, a collimator 133 in the form of a converging lens element, a stop 134, a beam splitter 136, a converging optical unit 138 in the form of a converging lens element, a detector 140 and a monitor 144. Evaluation unit 142.

  The measurement light source 132 emits measurement light 146, which is collimated by the collimator 133. The measuring light 146 passes through the beam splitter 136 and is focused by the focusing optical unit 138 to a point approximately at the center of the facet. Arrow k indicates the measurement direction, and arrows v and w indicate the spatial direction perpendicular thereto. When the facet 18 is not tilted with respect to the measurement direction k, the measurement light 146 ′ reflected from the facet 18 coincides with the incident measurement light 146. This corresponds to the angular position of the facet 18 as represented by the solid line in FIG. However, when the angular position of the facet 18 takes a value other than 0 ° with respect to the measurement direction k as indicated by a broken line in FIG. 9, the measurement light 146 does not reflect back from the facet 18 as it is, but is reflected measurement light. 146 ′ reflects along the principal ray direction k ′ that is offset from the principal ray direction of the reflected measurement light 146 ′ for the non-tilted facet 18. The reflected measurement light is collimated again by the focusing optics 138 and directed to the detector 140 by the beam splitter 136 in a parallel beam path. The reflected measurement light 146 ′ is detected as a disk by the detector 140, and the actual angular position of the facet 18 is evaluated as the displacement of the detected disk 148 relative to the reference disk 150 corresponding to the non-tilted angular position of the facet 18. Registered by unit 142.

  Accordingly, the displacement of the disk 148 relative to the reference disk 150 is proportional to the inclination of the facet 18 perpendicular to the measurement direction k.

  In the measurement method according to FIG. 9, the facets 18 of the facet mirror 14 (similarly to the facets 16 of the facet mirror 12) are individually and sequentially scanned in the form of dots.

  FIG. 10 shows a development of the measuring device 130 in FIG. 9 provided with the reference 130a in FIG. The elements of the measuring device 130a that are the same as or similar to the elements of the measuring device 130 in FIG. 9 are provided with the same reference numerals supplemented with a.

  The difference between the measurement device 130a and the measurement device 130 is in a modified form of the measurement light source 132a embodied as a distance sensor 156 capable of adjusting white light interference. The measurement light source 132 a has a cavity 160 that can be adjusted according to the arrow 158, and light from the light source 162 is supplied to the cavity 160. Light 164 reflected from the adjustable cavity 160 is coupled to a fiber or light guide 166 that emits light 164 as measurement light 146a at a location 168 corresponding to the location of the measurement light source 132 in FIG. Measurement device 130a further includes a spectrometer 170 to which a portion of reflected measurement light 146a is coupled via a fiber or optical waveguide 172, which evaluates this reflected measurement light by white light interferometry.

  As a result, the spatial position of the facet 18 in the direction of the normal to the facet 18 can also be measured by the measuring device 130a. In other words, in addition to the local angular position of the facet 18, the distance from the facet reflection point 174 is also measured by the color principle of the measuring device 130a. By adjusting the cavity 160, the angular position of the facet can be determined particularly precisely using the measured distance change.

  FIG. 11 shows a modification of the measuring device 130a provided with the reference symbol 130b. Elements of the measurement device 130b in FIG. 9 or the elements of the measurement device 130b that are the same as or similar to the elements of the measurement device 130a in FIG. 10 are provided with the same reference numerals supplemented with b.

  The difference between the measurement device 130b and the measurement device 130a in FIG. 10 is that the measurement light source 132b is implemented as a color distance sensor instead of a white light interference distance sensor. The measurement light source 132b includes a light source 180, a first optical waveguide 182, a second optical waveguide 184, a fiber coupler 186, and a measurement head 188 correspondingly. Although the structure including the condenser 133b, the focusing optical unit 138b, and the detector 140b is illustrated separately from the measurement head 188, the structure is ideally incorporated into the measurement head 188 (condenser). 133b and focusing optical unit 138b are already shown in the measuring head).

In this case, the surface 190 in FIG. 11 is an extracted surface of the facet 18 that can be measured particularly precisely even with respect to microroughness. The measurement range 192 from the wavelength λ _min to the wavelength λ _max is a measurement distance range that can be measured by the measurement light source 132b embodied as a color distance sensor. Thus, the measuring device 132b allows very precise combined angular position measurement and spatial position measurement of the reflecting surface of the facet 18 in the direction normal to the facet 18, i.e. normal to the facet 18.

  The measuring method and measuring device described above are based on the principle of deflectometry, but an optical method and an optical measuring device 200 for measuring the facet angular position of a facet mirror by interferometry are described below.

  The measurement device 200 includes a measurement light source 202, such as a laser, and an interferometer 204, such as a Twiman Green interferometer. The interferometer 204 includes a magnifying optical unit 206 for magnifying the measuring light 208, a beam splitter 210, an adjustable mirror 212, a cavity 214, a test optical unit 216, a detector 218, and a monitor 222. And an evaluation unit 220 provided.

  The measurement conditions during the interference measurement of the angular position of the facet 18 are almost the same as the measurement conditions during the measurement of the angular position of the facet 18 by the measurement device 110 in FIG. Evaluates the aerial image position, where the wavefront slope is evaluated by the evaluation unit 220. The center of the measurement light test wave is aligned with the midpoint of the facet 18 to be tested.

  The detector 218, eg, a camera, registers the fringe pattern 224 that appears as a result of the measurement light reflected from the facet 18 at the detector 218, rather than the measurement light spot, in contrast to the measurement device 110 in FIG. The actual angular position of facet 18 is registered as the slope of phase surface 226 relative to the reference phase surface. The inclination of the phase plane 226 is proportional to the displacement of the center of the wavefront of the measurement light 208 reflected from the facet 18 with respect to the focal point of the test optical unit 216 perpendicular to the measurement direction (see FIG. 8).

  The measurement method and the measurement device described above are based on the fact that the angular position of the facet of the facet mirror is measured in a state of being disassembled from the optical system using the facet mirror. A measurement method that can be performed in the assembled state is described below.

  FIG. 13A initially shows the mirror structure 10 from FIG. 1 and assumes that the mirror structure 10 has been incorporated into the optical system.

FIG. 13A also shows the mirror structure in FIG. In FIG. 13A, the result of precisely adjusting the angular position of the angular position and the facet 18 facet 16, the image of the facet 16 is imaged by overlapping centered relative to each other in the field plane F ₂ (image 22) . Next, FIG. 13B illustrates the effect of the actual angular position deviation from the desired angular position of facet 16b and / or the actual angular position deviation from the desired angular position of facet 18b. The actual displacement of the angular position of the actual deviation of the angular position and / or facet 18b of the facet 16b from the desired angular position, as indicated by arrow 21, the displacement of the image 22 in the viewing plane F _2, or beam offset Leads to.

  Therefore, the beam path of the EUV beam as shaped by the facet mirrors 12 and 14 will not correspond to the desired or required specifications.

In the method for measuring the angular position of the facets 16 and / or facets 18, the displacement of the image 22 according to FIG. 13b in the viewing plane F _2, registers and evaluated by a camera disposed there, or there close to.

In this case, each facet 16 is preferably measured individually. That is, the individual facets 16 of the field mirror 12 are selected, which can be done by a stop (not shown) or by tilting the remaining facets 16 in the case of tiltable facets. By the camera (not shown), to record the image 22, the displacement of the image 22 from the selected facet (e.g., facet 16b) desired position of the image of the actual angular position of the viewing plane F ₂ (FIG. 13A) Register as

  FIG. 14 shows a flowchart of a method for measuring the angular position of the facet of the facet mirror when the facet mirror is incorporated in an optical system.

  Measurement method 230 includes step 232 of attaching and pre-adjusting mirror structure 10 with facet mirrors 12 and 14, step 234 of incorporating mirror structure 10 into an optical system using mirror structure 10, and a desired angular position. Step 236 of measuring the angular position deviation of the individual facets 16 and / or 18 from the optical system and disassembling the mirror structure 10 from the optical system and using the actual angular position deviation from the desired angular position determined in advance. Re-adjusting the angular position of facets 16 and / or 18 at the adjustment station, and incorporating 240 the re-adjusted mirror structure into the optical system.

  As already mentioned above, all of the measurement methods described above also include adjusting the facets of the test facet mirror according to the results of the measurement of the angular position of the facets.

  FIG. 15 shows by way of example the adjustment of the facet 18 'of the facet mirror 14' having a body 19 '. The facet mirror 14 'is, for example, a specific configuration of the facet mirror 14 in FIG.

  Facet 18 'has a facet head 250, whose surface 252 forms the reflective surface of facet 18'.

  The facet 18 ′ further includes a shaft 254 on which the centering sleeve 256 and nut 258 are disposed. A disc spring 260 is disposed between the centering sleeve 256 and the body 19 ', and the spring is shown in plan view in FIG. 15A.

  The disc spring 260 has, for example, three spring legs 262, 264, and 266, and the outer ends thereof abut against the main body 19 '. In order to adjust the angular position of the facet 18 ', the nut is first tightened, with the result that the centering sleeve 256 is pressed against the disc spring 260 and the disc spring 260 is pressed against the body 19'. By tightening the nut 258, the angular position of the facet 18 'is adjusted by the displacement of the disc spring 260 relative to the body 19' and thus the pivoting of the shaft 154 of the facet 18 '. The angular position thus adjusted can then be fixed by a fixing means, for example by an adhesive.

  A method for measuring the facet of a facet mirror will be described with reference to FIGS. 16 and 17, in which case the facet of the facet mirror has at least two discontinuous tilt positions that can tilt the facet. Or the facets of the facet mirror have a continuous tilt position spectrum and the facets can be continuously tilted within the tilt position spectrum.

  The measurement task in this case consists in measuring the actual angular position relative to the desired angular position at each possible tilt position for each possible tilt position.

  If the facet has a discontinuous tilt position, the angular position must be measured at the corresponding discontinuous tilt position, and if the facet can take a continuous tilt position spectrum, the continuous tilt position The characteristic curve of operation must be determined.

  In principle, this measurement operation can be carried out using the method already described above, for example the measurement method according to FIG. 5 or the measurement method according to FIGS. 7 to 12, and the autocollimation measurement or diagram described above with reference to FIG. The retroreflection measurement method described with reference to 9-11 seems to be very suitable here.

  A measurement method for measuring the angular position of a tiltable facet is described below, but this method is particularly suitable for measuring the angular position at different tilt positions with the facet mirror incorporated into the optical system.

  FIG. 16 shows, by way of example, an individual facet 16 of the facet mirror 12 in FIG. 1 as a side view, with the facet 16 in the upper figure taking a first inclined position and the facet in the lower figure in FIG. 16 takes a second inclined position different from the first inclined position. The facet 16 has an actuation (not shown) that can tilt the facet 16 as desired between two tilt positions.

  In order to measure the actual angular position of the facet 16 with the tilt position switched as shown in the upper diagram of FIG. 16, the measurement light 270 is first directed to the first mirror array 272. The mirror array 272 has a plurality of first mirrors 274 whose angular positions can be adjusted, and the adjustability in the illustrated exemplary embodiment is centered about an axis perpendicular to the plane of the figure for simplicity. Is possible. From the first mirror array 272, the measurement light 270 is directed to the facet 16, from which the measurement light is directed to the second mirror array 276. The second mirror array again has a plurality of second mirrors 278 that can be adjusted with respect to angular position about an axis perpendicular to the plane of the drawing for simplicity as well.

  If the actual angular position of the facet 16 according to the lower diagram of FIG. 16 is intended to be measured at a different tilt position than that in the upper diagram of FIG. 16, the facet 16 is tilted accordingly to this different tilt position. At the same time, the mirrors 274 and 278 of the mirror arrays 272 and 276 are also tilted as shown with respect to the two mirrors 274a and 278a in the lower diagram of FIG. The tilt of the mirrors 274 and 278 of the mirror arrays 272 and 276 compensates for the tilt of the facet 16 so that the measurement light is only a small amount parallel to its beam path on the input side of the mirror array 272 and the output side of the mirror array 276 It will not displace and the corresponding measurement light source and the corresponding detector can be placed at a greater distance from the facet 16 and the detector need not have too much detector area.

  In FIG. 16, broken lines are used to indicate windows 280 and 282 that allow measurement light 270 to enter the vacuum region of the facet mirror when incorporated in the optical system.

  FIG. 17 shows a measuring device 290 that can be used to perform the method according to FIG. The measurement device 290 includes a measurement light source 292, a collimator 294, a switchable mirror array 272, a switchable mirror array 276, a focusing optical unit 296, and a detector 298. The switchable facet mirror 12 can be measured at different possible tilt positions of the provided facet 16 by means of the measuring device 290 described above in the state of being incorporated in an optical system.

  Depending on the tilt position of the facet 16, the mirror 274 of the switchable mirror array 272 and the mirror 278 of the switchable mirror array 276 are activated to compensate for the facet displacement of the facet 16.

  If all of the facets 16 are at a desired angular position at each set tilt position, exactly one point will appear on the detector, for example a camera, but the actual angular position of the facet 16 will be at each set tilt position. If there is a deviation from the desired angular position, a blurred point or points are imaged.

  Referring to FIGS. 18 and 19, still another aspect of the present invention relating to mounting a facet mirror structure such as mirror structure 10 on a mask inspection apparatus for inspecting a mask (reticle) for an EUV projection exposure apparatus will be described. explain.

  FIG. 18 shows such a mask inspection apparatus or mask inspection microscope 300 (no mirror structure 10) described in WO2009 / 118130.

  The mask inspection microscope 300 has an illumination module 302 that illuminates the mask 303 with EUV radiation. The mask inspection microscope 300 further includes an imaging optical unit 304 that forms an image by enlarging the illuminated portion of the mask 303 on the image plane BE, and a detector (CCD sensor) 305 is disposed on the image plane.

  The illumination module 302 includes a radiation source 306 and an illumination optical unit 307. The imaging optical unit 304 includes a mirror optical unit 308, which forms an image of the illumination portion of the mask 303 on the intermediate image plane ZE, and arranges a scintillator layer 309 on the intermediate image plane ZE, and expands downstream thereof. An optical unit 310 is arranged, which forms an intermediate image of the intermediate image plane ZE by enlarging it on the image plane BE.

  A facet mirror structure such as the mirror structure 10 according to FIG. 1 can then be incorporated into the illumination module 302 as an illumination optical unit 307.

  FIG. 19 shows yet another exemplary embodiment of a mask inspection apparatus 320 that can integrate the mirror structure 10 as an illumination optical unit. The mask inspection apparatus 320 is shown and described in FIG. 6 of International Publication No. 2011/012267 (there is no mirror structure 10). The mask inspection apparatus 320 includes four mirrors M1, M2, M3, and M4, which form an image on the image field 324 on the object plane 322 on which the mask to be inspected is arranged.

  Here, the mirror structure 10 can be used as an illumination optical unit for illumination of a mask disposed on the object plane 322.

Claims (49)

  Measure the angular position of the facets (16, 18; 18 ′) of the at least one facet mirror (12, 14) of the optical system designed for EUV application and then adjust the angular position according to the measured angular position Optical method, illuminating the facets (16, 18; 18 ') of the facet mirrors (12, 14) with measuring light (28; 62; 102; 124; 146; 146a; 146b; 208; 270) And detecting the measurement light (28; 62; 102; 124; 146; 146a; 146b; 208; 270) reflected from the facet (16, 18; 18 ') to register the actual angular position In an optical method for evaluating and then adjusting the angular position when the actual angular position deviates from the desired angular position, the facet (16; 1 The actual angular position, wherein the registering at least at the angular position spectrum of ± 10 ° with respect to a reference axis (24) of).   The method according to claim 1, wherein the actual angular position is registered with an angular position spectrum of at least ± 15 °, more preferably at least ± 20 °.   3. A method according to claim 1 or 2, characterized in that the angular position of the facet (16, 18; 18 ') is measured with the facet mirror (12, 14) removed from the optical system. .   3. A method according to claim 1 or 2, characterized in that the angular position of the facet (16, 18) is measured with the facet mirror (12, 14) incorporated in the optical system.   5. The method according to claim 1, wherein a plurality, preferably all, of the facets (16, 18) of the facet mirror (12, 14) are moved into the measuring beam (28; 62; 270). And simultaneously measuring the measuring light (28; 62; 270) reflected from the plurality, preferably all of the facets (16, 18).   5. The method according to claim 1, wherein the facets (16, 18) are individually and sequentially illuminated with the measuring light (102; 124; 146; 146a; 146b; 208; 270; 20). A method characterized by that.   7. A method according to any one of the preceding claims, characterized in that the angular position is measured by deflectometry.   The method according to any one of the preceding claims, characterized in that the spatial position of the facet (16, 18) is further measured in the direction of the normal to the facet (16, 18). The method according to claim 7 or 8, wherein the facet mirror (14) in a state incorporated in the optical system is a pupil mirror of a mirror structure (10), and the mirror structure (10) is: It further has a field mirror (12) disposed upstream of the pupil mirror (14), and the pupil mirror (14) is disposed between the field mirror (12) and a field surface (F ₂ ) disposed downstream. In the method, the measurement light (28) generated from one point (26) on the plane (F ₂ ) corresponding to the field surface (F ₂ ) in a state where the mirror structure is incorporated in the optical system is used as the mirror. The facet (18) of the pupil mirror (14) is directed to the pupil mirror (14) along the light beam path (20) that is identical to the working light beam path (20) during operation of the construction (10) and in the opposite direction. ) The light (28) is captured by the measurement surface (30), and the orientation and position of the measurement surface (30) are the orientation and position of the field mirror (12) in a state where the mirror structure (10) is incorporated in the optical system. A method characterized by corresponding to a position.   10. The method according to claim 9, wherein the actual angular position of the facet (18) of the pupil mirror (14) is determined in the measurement plane (30) by the facet (18) of the pupil mirror (14). Registration based on the actual light spot pattern (34) captured as a result of the reflection of the measurement light (28), and the angle offset of the facet (18) of the pupil mirror (14) as the actual light spot pattern. Registering by comparison with a desired light spot pattern, and then adjusting the facet (18) by the angular offset. 9. The method according to claim 7 or 8, wherein the facet mirror (12) in a state incorporated in the optical system is a field mirror (12) of the mirror structure (10), and the mirror structure ( 10) further includes a pupil mirror (14) disposed downstream of the field mirror (12), and the field mirror (12) and a field surface (F ₁ ) disposed upstream of the pupil mirror (14). The measurement light generated from one point (60) on the plane (F ₁ ) corresponding to the field surface (F ₁ ) in a state where the mirror structure (10) is incorporated in the optical system. (62) is directed to the field mirror (12) along the same light beam path (20) as the working light beam path (20) during operation of the facet mirror construction (10), and the field mirror (12) The facet (1 The measurement light (62) reflected from the measurement surface (64) is captured by the measurement surface (64), and the direction and position of the measurement surface (64) are determined based on the pupil mirror ( 14) corresponding to the orientation and position.   12. The method according to claim 11, wherein the actual angular position of the facet (16) of the field mirror (12) is determined by the facet (16) of the field mirror (12) on the measurement surface (64). Registration is made based on the actual light spot pattern (65) captured as a result of reflection of the measurement light (62), and the angle offset of the facet (16) of the field mirror (12) is changed to the actual light spot pattern ( 65) and a desired light spot pattern to register and the facet (16) is then adjusted by the angular offset.   9. The method according to claim 7 or 8, wherein the measuring light (102) is substantially perpendicular to the substantially center of the facet (16, 18) of the facet mirror (12, 14) as a measuring light beam having a point-like cross section. The measurement light beam that is sequentially directed at the incident and reflected from each of the facets (16, 18) is detected as a light spot (104), and the actual angular position of each of the facets (16, 18) is determined as a reference location ( 106) and registering it as a displacement of the location of the detected light spot (104) from 106).   9. The method according to claim 7 or 8, wherein the angular position of the facet (16, 18) is measured by autocollimation and the measuring light (124) is sent to the facet (16, 18) of the facet mirror (12, 14). The measurement light (124) illuminates each facet (16, 18) in a plane and focuses the measurement light (124) reflected from each facet (16, 18). A method characterized in that it is later detected as a measurement light spot (128) and the actual angular position of each facet (16, 18) is registered from the displacement of the measurement light spot (128) relative to a reference point (129).   9. The method according to claim 7 or 8, wherein the measuring light (146; 146a; 146b) is directed individually and sequentially to the facets (16, 18) and the measuring light (146; 146a; 146b) is first collimated and then focused on each facet (16, 18) at substantially normal incidence, the measurement light (146 ') reflected from each facet (16, 18) is collimated again, The collimated reflected measurement light (146 ′) is detected as a disk (148), and the actual angular position of each facet (16, 18) is displaced with respect to the reference disk (150). A method characterized by registering as:   16. The method according to claim 15, wherein a portion of the reflected measurement light (146 ′) is white light or in order to measure the spatial position of each facet (16, 18) in a direction normal to each facet. Detecting by colored light interferometry.   The method according to any one of claims 1 to 6, wherein the angular position of the facet (16, 18) is measured by interferometry, and the measuring beam (208) is measured by the interferometer (204). , 18) are sequentially directed individually, the measurement light (208) reflected from each facet (16, 18) is detected as an interference pattern (224), and the actual angular position of each facet (16, 18) Is registered as the slope of the phase plane (226) relative to the reference phase plane. 5. The method according to claim 4, wherein the facet mirror (14) in a state incorporated in the optical system is a pupil mirror (14) of the mirror structure (10), and the mirror structure (10) is: There is another facet mirror (12) which is a field mirror (12), and the pupil mirror (14) superimposes the facet (16) of the field mirror (12) on each other to obtain a field surface (F ₂ And at least one facet (18) of the pupil mirror (14) is assigned to each facet (16) of the field mirror (12), and the measurement light (20) is used as the use light of the optical system. Aiming to the field mirror (12) and the pupil mirror (14) along a beam path, selecting individual facets (16) of the field mirror, and selecting the selected of the field mirror (12) Asetto (16) and / or the actual angular position of the allocated facet (18) of the pupil mirror (14), the field plane said selected facet from a desired position of the image in the (F ₂₎ (16) And registering it as a displacement of the image.   19. Method according to claim 18, wherein the actual angular position of the selected facet (16) of the field mirror (12) and / or the assigned facet (18) of the pupil mirror (14) is determined on the pupil plane. A method further comprising registering the actual illumination deviation of the pupil plane from the desired illumination.   20. A method according to any one of the preceding claims, wherein the facets (16, 18) of the at least one facet mirror (12, 14) can tilt the facets (16, 18). A method having at least two discontinuous tilt positions.   20. A method according to any one of the preceding claims, wherein the facets (16, 18) of the at least one facet mirror (12, 14) have a continuous tilt position spectrum and the facets (16 , 18) can be continuously tilted within the tilt position spectrum.   22. Method according to claim 20 or 21, characterized in that the angular position of the facets (16, 18) is measured for different possible tilt positions.   23. The method according to any one of claims 20 to 22, wherein the measuring beam (270) is first applied to a first mirror array (272) having a plurality of first mirrors (274) with adjustable angular position. The measurement light (270) is directed from the mirror array (272) to the facet mirror (12, 14), and the measurement light (270) is angled from the facet mirror (12, 14). The first mirror (274) is directed to a second mirror array (276) having a plurality of adjustable second mirrors (278) to compensate for tilt of the facets (16, 18) during angular position measurement. ) And the second mirror (278) according to a set tilt position of the facets (16, 18).   24. A method as claimed in any one of the preceding claims, wherein the facets (18 ') are individually pivotally arranged on the body (19') of the facet mirror (14 ') and the facets (18'). ') Each having a shaft (254) for passing through the body (19') and seating a centering sleeve (256) and a nut (258) and having a plurality of spring legs (262, 264, 266) A spring (260) is disposed between the centering sleeve (256) and the body (19 ′), and the nut (258) is tightened for the purpose of adjusting the angular position of each facet (18 ′). The shaft (254) is pivoted by the displacement of the disc spring (260) relative to the body (19 ′) and, if appropriate, the adjusted angular position is fixed by a fixing means such as adhesive Method characterized in that subsequently fixed using.   An optical measuring device for measuring the angular position of the facets (16, 18; 18 ') of at least one facet mirror (12, 14) of an optical system designed for EUV applications, the facet (16 , 18; 18 ′) with a measuring light source (27; 74; 92; 132; 132a; 132b; 202) that illuminates with measuring light (28; 62; 102; 124; 146; 146a; 146b; 208; 270); A detector for detecting the measurement light (28; 62; 102; 124; 146; 146a; 146b; 208; 270) reflected from the facet (16, 18; 18 '); and the facet (16, 18; 18). ') To detect the actual angular position of the detected measuring light (28; 62; 102; 124; 146; 146a; 14 b; 208; 270) in an optical measuring device comprising an evaluation unit (98; 120; 142; 142a; 142b; 220), said measuring device (40; 70; 90; 110; 130; 200; 290) ) Designed to register the actual angular position of the facets (16, 18; 18 ′) with an angular position spectrum of at least ± 10 ° with respect to the reference axis (24).   26. A measuring device according to claim 25, designed to register the actual angular position with an angular position spectrum of at least ± 15 °, more preferably at least ± 20 °.   27. Measuring device according to claim 25 or 26, in order to measure the angular position of the facet (16, 18; 18 ') with the facet mirror (12, 14) removed from the optical system. A measuring device that is embodied as:   27. Measuring device according to claim 25 or 26, in order to measure the angular position of the facet (16, 18; 18 ') with the facet mirror (12, 14) incorporated in the optical system. A measuring device, characterized in that it is integrated in or capable of being integrated into a system.   29. Measuring device according to any one of claims 25 to 28, wherein the measuring light source (27; 74; 292) is a plurality, preferably all, of the facets (16, 16) of the facet mirror (12, 14). 18) is simultaneously illuminated with the measuring light (28; 62; 270), and the detector (44; 76; 298) reflects the measuring light reflected from the plurality, preferably all of the facets (16, 18). (28; 62; 270) is simultaneously detected.   29. A measuring device according to any one of claims 25 to 28, wherein the measuring light (92; 132; 132a; 132b; 202) causes the facet to pass through the measuring light (102; 124; 146; 146a; 146b; 208) and individually illuminating individually in 208), and the measurement light source and the detector are both movable.   The measuring device according to any one of claims 25 to 30, wherein the angular position is measured by deflectometry.   32. A measuring device according to any one of claims 25 to 31, wherein a distance sensor (132a; 132b) measures the spatial position of the facets (16, 18) in the direction of the normal to the facets (16, 18). A measuring device further comprising: 33. The measuring device according to claim 31 or 32, wherein the facet mirror (14) in a state incorporated in the optical system is a pupil mirror (14) of a mirror structure (10), and the mirror structure ( 10) has the pupil mirror (14) a viewing mirror (12) disposed on the upstream addition of the pupil mirror (14) said field mirror (12) and the viewing surface that is positioned downstream and _{(F 2)} The measurement light source (27) is a point on a plane (F ₂ ) corresponding to the field surface (F ₂ ) in a state where the mirror structure (10) is incorporated in the optical system. The measurement light (28) generated from (26) is the same as the used light beam path (20) during operation of the mirror structure (10), and the pupil mirror (14) along the light beam path in the opposite direction. ) In order to capture the measurement light (28), which is a light source and reflected from the facet (18) of the pupil mirror (14), on the measurement surface (30), a measurement reticle (32) is disposed, and the measurement surface (30 ) Corresponds to the direction and position of the field mirror (12) in a state in which the mirror structure (10) is incorporated in the optical system.   34. The measurement device according to claim 33, wherein the detector (44) is a result of reflection of the measurement light (28) at the facet (18) of the pupil mirror (14) at the measurement reticle (32). The captured actual light spot pattern (34) is detected and the evaluation unit registers the actual offset to register the angle offset of the facet (18) of the pupil mirror (14) by comparison with the desired light spot pattern. A measuring device, characterized by evaluating a light spot pattern (34). 33. The measuring device according to claim 31 or 32, wherein the facet mirror (12) in a state incorporated in the optical system is a field mirror (12) of the mirror structure (10), and the mirror structure (10) further includes a pupil mirror (14) disposed downstream of the field mirror (12), and a field surface (F ₁ ) in which the field mirror (12) is disposed upstream of the pupil mirror (14). in the measurement device arranged between said measurement light source (74) is in the plane (F ₁₎ corresponding to the viewing surface the mirror structure (10) in a state incorporated in the optical system (F ₁₎ The measurement light (62) generated from one point (60) is directed to the field mirror (12) along the same light beam path as the used light beam path (20) during operation of the facet mirror structure (10). Oriented In order to capture the measurement light (62) reflected from the facet (16) of the field mirror (12) by the measurement surface (64), a measurement reticle (66) is arranged, and the measurement plane (64) The direction and position correspond to the direction and position of the pupil mirror (14) in a state where the mirror structure (10) is incorporated in the optical system.   36. The measurement device according to claim 35, wherein the detector (76) is a result of reflection of the measurement light (62) at the facet (16) of the field mirror (12) at the measurement reticle (66). The captured actual light spot pattern (65) is detected, and the evaluation unit registers the actual offset to register the angle offset of the facet (18) of the field mirror (12) by comparison with a desired light spot pattern. A measuring device, characterized by evaluating the light spot pattern (65).   Measuring device according to claim 31 or 32, wherein said measuring light source (92) emits a measuring light beam (102) having a point-like cross section, said measuring light beam (102) being said facet mirror (12, 14) is directed sequentially at substantially normal incidence to approximately the center of the facet (16, 18), and the detector (96) reflects the measurement light beam (102 ′) reflected from each facet (16, 18). ) As a light spot (104), and the evaluation unit (98) determines the actual angular position of each facet (16, 18) as the location of the detected light spot (104) from a reference location (106). A measuring device, which is registered as a deviation.   33. The measuring device according to claim 31 or 32, comprising an autocollimation optical unit (112), wherein the measuring light source causes the facet (16, 18) of the facet mirror (12, 14) to pass through the measuring light (124). The detector (118) sequentially illuminates the surface with the focusing optical unit (116) after focusing the measurement light (124 ') reflected from the facets (16, 18) by the focusing optical unit (116). (128), and the evaluation unit (120) registers the actual angular position of each facet (16, 18) from the displacement of the measurement light spot (128) with respect to a reference point (129). And measuring device.   33. A measuring device according to claim 31 or 32, wherein the measuring light source (312; 132a; 132b) is pointed to sequentially point the measuring light (146; 146a; 146b) individually to the facets (16, 18). It is embodied as a light source, and collimators (133; 133a; 133b) for collimating the measurement light (146; 146a; 146b) in the measurement light beam path, and the measurement light (146; 146a; 16 and 18) and a focusing optical unit (138; 138a; 138b) for focusing at substantially normal incidence, and the measuring light (146 ') reflected from each facet (16, 18) is the focusing optical unit. (138; 138a; 138b) and collimated again, the detector (140; 140a; 14 b) detects the collimated reflected measurement light (146 ′) as a disc (148), and the evaluation unit (142; 142a; 142b) determines the actual angular position of each of the facets (16, 18). A measuring device, which is registered as a displacement of the detected disc (148) with respect to a reference disc (150).   40. Measuring device according to claim 39, characterized in that the measuring light source (132a; 132b) comprises an adjustable distance sensor.   A measuring device according to any one of claims 25 to 30, wherein the angular position of the facets (16, 18) is measured by interferometry, there is an interferometer (204), and the measuring light source (202) is The measurement light (208) is individually and sequentially directed to the facets (16, 18) through the interferometer (204), and the detector (218) reflects the measurement light reflected from each facet (16, 18). (208) is detected as an interference pattern (224), and the evaluation unit (220) registers the actual angular position of each facet (16, 18) as the slope of the phase plane (226) relative to a reference phase plane. Measuring device characterized by. 29. The measuring device according to claim 28, wherein the facet mirror (14) in a state incorporated in the optical system is a pupil mirror (14) of the mirror structure (10), and the mirror structure (10) is , Further comprising a facet mirror (12) which is a field mirror (12), and the pupil mirror (14) superimposes the facet (16) of the field mirror (12) on each other to obtain a field surface (F ₂ ), at least one facet (18) of the pupil mirror (14) is assigned to each facet (16) of the field mirror (12), and the measurement light source converts the measurement light into the optical Directed to the field mirror (12) and the pupil mirror (14) along the used light beam path (20) of the system, the individual facets (16) of the field mirror (12) selected Is, as a detector, the camera is arranged on or near the said viewing surface (F _2), the camera records an image of the selected facet (16), the evaluation unit, the field mirror (12 ) Of the selected facet (16) and / or the assigned facet (18) of the pupil mirror (14) from the desired position of the image (22) in the field plane (F ₂ ). Registering the displacement of the image (22) of the selected facet (16).   43. A measuring device according to claim 42, wherein a further detector in the form of a camera is arranged at or near the pupil plane, the camera records the illumination of the pupil plane, and the evaluation unit comprises the field of view. The actual angular position of the selected facet (16) of the mirror (12) and / or the assigned facet (18) of the pupil mirror (14) is determined from the actual illumination of the pupil plane from the desired illumination of the pupil plane. A measuring device that is registered as a deviation of illumination.   44. A measuring device according to any one of claims 25 to 43, wherein the facets of the at least one facet mirror (12, 14) are capable of tilting the facets (16, 18). The facet (16, 18) of the at least one facet mirror has a continuous tilt position spectrum, and the facet (16, 18) is continuous in the tilt position spectrum. The measuring device (40; 70; 90; 110; 130; 130a; 130b; 200; 290) can be measured for possible tilt positions with different angular positions of the facets (16, 18). Measuring device, characterized by being designed to   45. The measuring device according to claim 44, wherein a first mirror array (272) having a plurality of first mirrors (274) capable of adjusting an angular position and a plurality of second mirrors (278) capable of adjusting an angular position. A second mirror array (276) having the facet (16) and the first mirror (274) and the second mirror (278) to compensate for the tilt of the facet (16, 18) during angular position measurement. , 18) and a controller for tilting according to the set tilt position.   Use of a facet mirror arrangement (10) in an illumination device of a mask inspection apparatus (300; 320) for EUV lithography.   47. Use according to claim 46, wherein the facet mirror arrangement (10) comprises at least one first facet mirror (12) having a plurality of first facets (16) and a plurality of second facets (18). Use with two second facet mirrors (14).   48. Use according to claim 47, wherein the first facet (16) is embodied in the form of an elongated arch and / or the second facet (18) is embodied in the form of a stamp.   49. Use according to claim 47 or 48, wherein the first facet mirror (12) is arranged in a plane conjugate to the field plane on which the mask to be inspected is arranged and the at least one second facet mirror (14). ) Placed in a plane conjugate to the pupil plane.