DE102022213078A1 - Measuring device for measuring reflection properties - Google Patents

Abstract

A measuring device (10; 110; 340; 410) for measuring reflection properties of a sample (12) comprises a radiation source (14) for providing a measuring radiation (16), an optical beam shaping system (42; 142; 342; 442) which is configured to generate from the measuring radiation a plurality of measuring beams (30-1, 30-2) directed at different locations (18-1, 18-2) of the sample, and is further configured to set a wavelength of the measuring beams. The measuring device further comprises a detector (46) for detecting radiation (147) of the measuring beams reflected on the sample.

Description

Background of the invention

The invention relates to a measuring device for measuring reflection properties of a sample and a method for measuring reflection properties of such a sample.

Such measuring devices can be designed as reflectometers, which are usually used to describe measuring devices for determining the degree of reflection of a sample for electromagnetic radiation. The degree of reflection, also called reflectivity, is the ratio between the intensity of the reflected electromagnetic radiation and the intensity of the incident electromagnetic radiation. The degree of reflection depends in particular on the angle of incidence and the wavelength of the incident radiation and on the material properties and structures of the reflecting surface. By taking measurements at different wavelengths in a given wavelength range, reflection spectra can be recorded, which can be used to determine the properties of the materials involved in the reflection and their structure.

Such measurements are used, for example, to determine the optical properties of mirrors for microlithography in the extreme ultraviolet wavelength range (EUV) with an operating wavelength of about 13.5 nm or about 6.8 nm. Such a measuring device is used, for example, in US6,856,395B2 described. The measurement of reflectivity should often be carried out with a high local resolution. The necessary measurement of a large number of measuring points on the sample is very time-consuming and therefore correspondingly costly.

Underlying task

It is an object of the invention to provide a device and a method by which the aforementioned problems are solved and, in particular, the measurement of the reflection properties can be carried out with reduced expenditure of time.

Inventive solution

The above-mentioned object can be achieved according to the invention, for example, with a measuring device for measuring reflection properties of a sample. The measuring device according to the invention comprises a radiation source for providing a measuring radiation, an optical beam shaping system which is configured to generate several measuring beams from the measuring radiation, which are directed at different locations on the sample. Furthermore, the optical beam shaping system is configured to set a wavelength of the measuring beams. In addition, the measuring device comprises a detector for detecting radiation from the measuring beams reflected on the sample.

The measuring beams are directed at different locations on the sample, i.e. each measuring beam hits a different location on the sample. The measuring beams are each individual measuring beams, i.e. they can be distinguished from one another and are not rays of a continuous beam. By adjusting the wavelength, the measuring beams are essentially monochromatic, i.e. they have a narrow spectral width.

By generating several measuring beams aimed at different locations on the sample, the measurement of the reflection properties of the sample can be parallelized, i.e. several measuring locations on the sample are measured simultaneously. This reduces the time required for closely spaced measurement of the samples.

According to one embodiment, the optical beam forming system is configured to generate the measuring beams by splitting an input beam containing the measuring radiation.

According to a further embodiment, the measuring device is configured for wavelength-dependent measurement of the reflection properties of the sample and the optical beam shaping system is further configured to set a wavelength of the measuring beams. The optical beam shaping system thus serves as a monochromator.

According to a further embodiment, the beam shaping system is configured to vary the wavelength of the measuring beams. According to one embodiment, the beam shaping system is configured to vary the wavelength of the measuring beams over a wavelength range of at least 1 nm or at least 2 nm, for example over the wavelength range extending from approximately 6 nm to approximately 18 nm, in particular the wavelength range extending from approximately 12.5 nm to approximately 15.0 nm.

According to a further embodiment, the measuring device further comprises an evaluation device which is configured to determine the reflection properties of the sample at the different locations simultaneously from the reflected radiation of the measuring beams detected by the detector. In other words, the reflection properties are determined in parallel at several locations on the sample.

According to a further embodiment, the optical beam shaping system is configured to generate the measuring beams directed at different locations on the sample one after the other.

According to a further embodiment, the optical beam shaping system comprises an aperture which is configured to let through at least a first of the measuring beams and at the same time to block at least one further of the measuring beams, wherein the aperture is mounted such that it can be moved between at least two positions at which either the first measuring beam or the further measuring beam is let through. According to one embodiment, the beam shaping system comprises a splitting module for splitting the input beam into the various measuring beams and the aperture is arranged downstream of the splitting module in the beam path of the measuring radiation. According to one embodiment, the aperture only comprises one opening for letting through one of the measuring beams, wherein at the first of the two positions the first measuring beam passes through the opening and at the second position the further measuring beam passes through the opening.

According to a further embodiment, the optical beam shaping system comprises a grating structure for generating the measuring beams directed at the different locations on the sample from the measuring radiation. This means that the grating structure serves to split the incoming measuring radiation into the individual measuring beams. According to a further embodiment, a Fresnel prism can also be used instead of the grating structure.

According to a further embodiment, the optical beam shaping system comprises a further grating structure for adjusting the wavelength of the measuring beams.

According to a further embodiment, the further grid structure is arranged transversely to the first grid structure. This means that the lines of the second grid structure run transversely to the lines of the first grid structure. According to one embodiment, the lines of the second grid structure are arranged perpendicular to the lines of the first grid structure.

According to a further embodiment, the first grid structure and the further grid structure form a two-dimensional grid.

According to a further embodiment, the first grating structure and the further grating structure are arranged at different locations in the beam path of the measuring radiation within the beam shaping system.

According to a further embodiment, the first grating structure is arranged downstream of the further grating structure in the beam path of the measuring radiation within the beam shaping system.

According to a further embodiment, the measuring device further comprises an imaging optics which is arranged in a beam path of the reflected radiation between the sample and the detector. In other words, the imaging optics are arranged in a beam path which is formed by the reflected radiation during measurement operation, between the sample and the detector. According to one embodiment, the measuring device comprises a sample holder for holding the sample and the imaging optics are arranged between the sample holder and the detector. According to a further embodiment, the imaging optics are configured to image a surface section of the sample illuminated by the measuring radiation onto the detector.

According to a further embodiment, the radiation source is configured to generate the measuring radiation in the EUV wavelength range. This means that the measuring radiation is EUV radiation. The EUV radiation can be generated, for example, by means of a pulsed Nd-YAG laser, the laser beam of which is focused on a gold target or another suitable material. The laser beam generates a plasma on the surface of the gold target, which emits a quasi-continuous spectrum of electromagnetic radiation in the EUV range.

According to a further embodiment, the beam-forming system comprises a beam splitting module for splitting an input beam containing the measuring radiation into the measuring beams, wherein the measuring device further comprises a first airtight chamber in which at least one module of the measuring device arranged in a beam path of the measuring radiation is arranged, and a further airtight chamber in which the beam splitting module is arranged. This makes it possible to replace the beam splitting module without affecting the atmosphere of the first airtight chamber.

According to one embodiment, the beam splitting module is arranged, possibly next to a diaphragm, in particular a slit diaphragm, as the only optical module in the beam path of the measuring radiation in the further airtight chamber. The airtight chamber is advantageously configured to detect an atmospheric state, in particular to maintain a vacuum, such as a high vacuum, inside them. In this case, when the beam splitting module is replaced, any vacuum that may exist in the first airtight chamber can be maintained, ie this vacuum does not have to be specifically released.

Preferably, the airtight chambers each have one or more optical windows which are configured to allow the measuring radiation to pass through. The module of the measuring device arranged in the beam path of the measuring radiation can include the radiation source, the detector and/or a sample holder. According to one embodiment, the measuring device comprises its own airtight chamber for the radiation source.

According to a further embodiment, the module of the measuring device arranged in the first airtight chamber is a further module of the beam forming system.

According to a further embodiment, the measuring device is configured to measure the reflection properties of an optical element for microlithography. According to one embodiment, the measured optical element is an element of a projection exposure system for microlithography, for example a projection lens of the projection exposure system.

According to the invention, a measuring device for measuring reflection properties of a sample is also provided. This measuring device comprises a radiation source for providing a measuring radiation, an optical beam shaping system which is configured to generate at least one measuring beam directed at the sample from the measuring radiation. The measuring device is also configured to set a wavelength of the measuring beam. The measuring device also comprises a detector for detecting radiation of the measuring beams reflected on the sample and an imaging optics which is arranged in a beam path of the reflected radiation between the sample and the detector. This measuring device can be designed in one of the embodiments or embodiment variants described above.

In other words, the imaging optics of the last-described measuring device are arranged between the sample and the detector in a beam path that is formed by the reflected radiation during measurement operation. According to one embodiment, the measuring device comprises a sample holder for holding the sample and the imaging optics are arranged between the sample holder and the detector. According to one embodiment, the imaging optics are configured to image a surface section of the sample illuminated by the measuring radiation onto the detector.

By providing imaging optics, the numerical aperture of the detector-side beam path, which guides the measuring radiation reflected from the sample by irradiation with the measuring beam, can be selected to be relatively large, so that scattered light generated on the sample surface can also be detected by the measuring detector. This enables improved measurement accuracy.

The above-mentioned object can also be achieved, for example, with a method for measuring reflection properties of a sample. This method comprises generating several measuring beams directed at different locations on the sample, setting a wavelength of the measuring beams, and detecting radiation from the measuring beams reflected on the sample. The reflection properties of the sample are preferably determined using the detected reflected radiation from the measuring beams.

According to one embodiment, the sample is an optical element for microlithography, such as an optical element of a projection exposure system for microlithography.

The features specified with regard to the above-mentioned embodiments, examples or variants, etc. of the measuring device according to the invention can be transferred accordingly to the measuring method according to the invention and vice versa. These and other features of the embodiments according to the invention are explained in the description of the figures and the claims. The individual features can be implemented either separately or in combination as embodiments of the invention. Furthermore, they can describe advantageous embodiments that are independently protectable and whose protection may only be claimed during or after the application has been filed.

Short description of the drawings

• 1 eine Seitenansicht einer ersten Ausführungsform einer Messvorrichtung zur Vermessung von Reflexionseigenschaften einer Probe,
• 2 die Messvorrichtung gemäß 1 in Draufsicht,
• 3 einen Abschnitt einer weiteren Ausführungsform einer Messvorrichtung zur Vermessung von Reflexionseigenschaften einer Probe in Draufsicht,
• 4 einen Abschnitt einer weiteren Ausführungsform einer Messvorrichtung zur Vermessung von Reflexionseigenschaften einer Probe in Seitenansicht,
• 5 eine Draufsicht einer weiteren Ausführungsform einer Messvorrichtung zur Vermessung von Reflexionseigenschaften einer Probe,
• 6 eine Seitenansicht einer weiteren Ausführungsform einer Messvorrichtung zur Vermessung von Reflexionseigenschaften einer Probe, sowie
• 7 eine schematische Ansicht einer Projektionsbelichtungsanlage für die Mikrolithographie mit einer Vielzahl an Spiegelelementen, welche als Probe zur Vermessung mit einer der in den 1 bis 3 dargestellten Messvorrichtungen dienen können.

The above and other advantageous features of the invention are illustrated in the following detailed description of exemplary embodiments or embodiments according to the invention with reference to the attached schematic drawings. It shows:

• 1 a side view of a first embodiment of a measuring device for measuring reflection properties of a sample,
• 2 the measuring device according to 1 in plan view,
• 3 a section of another embodiment of a measuring device for measuring reflection properties of a sample in plan view,
• 4 a section of another embodiment of a measuring device for measuring reflection properties of a sample in side view,
• 5 a plan view of another embodiment of a measuring device for measuring reflection properties of a sample,
• 6 a side view of another embodiment of a measuring device for measuring reflection properties of a sample, and
• 7 a schematic view of a projection exposure system for microlithography with a large number of mirror elements, which can be used as a sample for measurement with one of the 1 to 3 shown measuring devices can be used.

Detailed description of embodiments according to the invention

In the embodiments or embodiments or variants described below, functionally or structurally similar elements are provided with the same or similar reference numerals as far as possible. Therefore, in order to understand the features of the individual elements of a specific embodiment, reference should be made to the description of other embodiments or the general description of the invention.

To facilitate the description, a Cartesian xyz coordinate system is shown in the drawing, from which the respective positional relationship of the components shown in the figures results. In 1 the z-direction runs perpendicular to the drawing plane, the x-direction to the right and the y-direction upwards.

1 shows a schematic side view of a first embodiment 10 of a measuring device in the form of a reflectometer for measuring reflection properties of a sample 12 or a test object. The measuring device 10 is configured to detect a degree of reflection at a plurality of wavelengths in the EUV spectral range. For this purpose, a radiation source 14 generates a measuring radiation 16 preferably in the EUV wavelength range. Furthermore, the measuring device 10 is configured to simultaneously measure different measuring locations 18-1, 18-2 on the sample 12 and to set a predetermined angle of incidence α (reference number 19) of the measuring radiation 16 on the sample 12 (cf. 2 ). To adjust the angle of incidence α, a sample holder 11 is mounted so as to be rotatable with respect to a rotation axis parallel to the y-axis (see reference numeral 13). This allows the angle of incidence α on the sample 12 held by the sample holder 13 to be varied in a plane parallel to the xz-plane.

The sample 12 is, for example, a mirror for a projection exposure system for EUV microlithography, in particular a mirror of a projection objective or of an illumination system of the projection exposure system. Such a projection exposure system is described below with reference to 4 described.

The radiation source 14 of the measuring device comprises, for example, a source based on laser-produced plasma (LPP) with a pulsed laser, the laser beam of which generates a plasma on a gold target. The plasma emits a quasi-continuous spectrum of EUV radiation in the wavelength range of less than 100 nm, preferably in the wavelength range of approximately 6 nm to approximately 18 nm, as an emission spot. The EUV radiation generated in this way serves as measuring radiation 16.

The measuring device 10 also comprises an input aperture 20 and a collecting optics in the form of a collecting mirror 22. The input aperture 20 is arranged downstream of the radiation source 14 and serves to limit the beam of the measuring radiation 16 emitted by the radiation source 14. After passing through the input aperture 20, the measuring radiation 16 strikes the collecting mirror 22, thereby forming a converging beam 23. According to one embodiment, the collecting mirror 22 is a plane-elliptical mirror. Plane-elliptical mirrors are mirrors with a reflective surface that is flat in one direction and in the form of an ellipse in a direction substantially perpendicular to it. The collecting mirror 22 directs the measuring radiation 16 onto a reflection grating 24 and is configured in such a way that the emission spot is preferably enlarged and the beam divergence is reduced.

The reflection grating 24 is configured as a two-dimensional grating 25. This comprises a grating support and two grating structures arranged thereon, namely a first grating structure 26 in the form of a line grating with horizontal grating lines and a second grating structure 28 in the form of a line grating oriented transversely to the line grating of the first grating structure 26. In the embodiment shown, the line grating of the second grating structure 28 is oriented perpendicular to the line grating of the first grating structure 26, ie it contains vertical Grid lines. The grid lines of the grid structures 26 and 28 have a constant line density. In the present embodiment, the line density is at least 1000 lines per mm, e.g. 1600 lines per mm.

The first grating structure 26 serves to split the measuring radiation 16 radiated onto the reflection grating 24 into several measuring beams 30. The reflection grating 24 is therefore also referred to in this text as a beam splitting module. In 1 Two such measuring beams 30-1 and 30-2 are shown. These are directed at the different measuring locations 18-1 and 18-2 on the sample 12 mentioned above. The measuring beams 30 spread out in different directions parallel to the yz plane, pass through respective passage openings 34-1 and 34-2 of an exit aperture 32, are reflected by a further collecting mirror 36, pass through a beam splitter 38 and then impinge on the measuring locations 18-1 and 18-2 of the sample 12.

The second grating structure 28 serves to set a wavelength of the measuring beams 30-1 and 30-2. The beam 23 of the measuring radiation 16 radiated onto the reflection grating 24 is focused by diffraction along a focal line which is oriented parallel to the z-axis. Alternatively, a Fresnel prism can be used instead of the first grating structure 26 for the function of splitting the beam 23 into several measuring beams 30.

In 2 the measuring device 10 is shown in plan view, ie in the xz plane. As can be seen therein, the measuring radiation 16 is reflected by the second grating structure 28 in a wavelength-dependent manner such that a wavelength-dependent intermediate focus 40 of the measuring beams 30-1 and 30-2 is located at the location of the exit aperture 32, ie in the beam path in front of the collecting mirror 36. This intermediate focus 40 is in the 2 The view shown parallel to the xz plane is identical for both measuring beams 30-1 and 30-2.

The exit aperture 32 has an exit slit parallel to the xz plane with a narrow slit width, whereby only a very small wavelength range of the measuring radiation 16 can pass around a test wavelength. The slit width of the exit aperture 32 in the xz plane is adjustable according to one embodiment and determines the respective measuring spot size of the measuring beams 30-1 and 30-2 on the sample 12 and the spectral resolution. The reflection grating 24 is mounted so as to be tiltable parallel to the y-axis (see reference numeral 48 in 2 ). The test wavelength can be changed by tilting the reflection grating 24 accordingly.

The collecting mirror 36 is configured and arranged such that the respective exit slit of the exit aperture 32 is imaged on the sample 12. According to one embodiment, the collecting mirror 36 is configured such that the exit slit is also enlarged and imaged onto the sample 12 with reduced beam divergence.

The combination of the collecting mirror 22, the reflection grating 24, the exit aperture 32 and the collecting mirror 36 thus forms a beam shaping system 42 which is configured to generate the measuring beams 30-1 and 30-2 directed at the different measuring locations 18-1, 18-2 from an input beam in the form of the convergent beam 23 after passing through the input aperture 20 and is also configured to set the test wavelength of the measuring beams 30-1 and 30-2. Due to the latter function, the beam shaping system 42 can also be referred to as a monochromator.

A portion of the respective measuring radiation 16 of the measuring beams 30-1 and 30-2 is directed to a reference detector 44 when passing through the beam splitter 38, as can be seen from 2 This detects an associated reference intensity for each of the measuring beams 30-1 and 30-2. The intensity of the measuring radiation 47 reflected by the sample 12 at the measuring locations 18-1 and 18-2 is detected by a measuring detector 46 as the respective measuring intensity.

Using the measurement and reference intensities recorded for the individual measurement beams 30-1 and 30-2, the reflectance of the test object 12 is determined with respect to a set angle of incidence α at the different measurement locations 18-1 and 18-2 as a function of the test wavelength determined by the beam shaping system 42 by means of an evaluation device 66. The measuring device 10 thus enables a parallelized, i.e. simultaneous, measurement of the reflectance with respect to the measurement locations 18. As mentioned above, the first grating structure 26 of the reflection grating 24 can generate more than two measurement beams 30, in particular more than five or more than ten measurement beams 30, and thus a correspondingly large number of measurement locations 18 can be measured simultaneously.

In addition to the above-mentioned rotary bearing for adjusting the angle of incidence α, the sample holder 11 has a bearing for displacement in the y- and z-direction (see reference numerals 50 and 52 in the 1 and 2 ). This allows the sample 12 to be moved to another position after a first reflectivity measurement and then further measuring locations 18 on the sample can be measured.

The measuring device 10 comprises a plurality of airtight chambers 54, 56, 58 and 60 in the form of vacuum chambers. According to one embodiment In this embodiment, they are each designed to produce a high vacuum. The radiation source 14 and the entrance aperture 20 are arranged in the first airtight chamber 54, the collecting mirror 22, the beam splitter 38 and the reference detector 44 in the second airtight chamber 56 and the sample 12 and the sample holder 11 in the third airtight chamber 58.

The reflection grating 24 and the exit aperture 32 are arranged in a fourth airtight chamber 60, which is partially surrounded by the second airtight chamber 56 and comprises an access flap 64. Thus, in each of the chambers 54, 56, 58, 60 and 62 at least one module of the measuring device is arranged in the beam path of the measuring radiation 16. In the 1 and 2 In the embodiment shown, two of the modules comprising the beam shaping system 42, namely the collecting mirrors 22 and 36, are not contained in the chamber 60.

The access flap 64 serves to gain access to the interior of the chamber 60, for example to replace the reflection grating 24 and/or the exit aperture 32 without disturbing the atmosphere of the chamber 56. This allows access to the reflection grating 24 and/or the exit aperture 32 without changing the air pressure in the chamber 56. This makes it possible to replace the reflection grating 24 and/or the exit aperture 32 with little effort.

The collecting mirror 36 can be arranged in the chamber 56 or in a separate chamber 62, which, analogous to the chamber 60, is partially surrounded by the chamber 56 and also includes an access flap 64. This also allows the collecting mirror 36 to be replaced with little effort if necessary.

Optical windows 63 that are permeable to the measuring radiation 16 are arranged at suitable locations in the walls of the chambers 54, 56, 58, 60 and, if applicable, 62, so that the beam path of the measuring radiation 16 remains undisturbed within the measuring device 10.

In 3 A further embodiment 110 of a measuring device is shown schematically, which differs from the embodiment 10 according to 1 only differs in the section located in the airtight chamber 58. Therefore, in 3 only the airtight chamber 58 is shown, analogous to the 2 in top view. As 3 As can be seen, the chamber 58 in this embodiment is longer in the x-direction than the chamber according to 2 . The beam forming system 42 is thus configured so that the beam paths of the measuring beams 30-1 and 30-2 are slightly less convergent than in 2 .

The section in the airtight chamber 58 according to 3 differs from the corresponding section under 2 that an imaging optics 157 is arranged between the sample 12 held by the sample holder 11 and the measuring detector 46. The imaging optics 157 is configured to image the surface sections on the sample 12 illuminated by the measuring beams 30-1 and 30-2 onto the measuring detector 46. For this purpose, the imaging optics 157 comprises, according to one embodiment variant, several mirror elements, for example two mirror elements 159-1 and 159-2, as in 3 shown.

The measuring radiation 147 reflected from the sample surface forms a beam path within the imaging optics 157. In 3 For better clarity, only the beam path for imaging the surface section illuminated by the measuring beam 30-1 is shown. The surface section illuminated by the measuring beam 30-2 is imaged at a location on the measuring detector 46, which is offset in the y-direction relative to the location on the measuring detector 32 at which the surface section illuminated by the measuring beam 30-1 is imaged.

The embodiment according to 3 has compared to the embodiment according to the 1 and 2 more freedom in the use of the installation space in the area of the sample holder 11. Furthermore, this can ensure that even with relatively large dimensions of the surface sections of the sample 12 illuminated by the measuring beams 30-1 and 30-2, the associated sections can be detected separately from one another on the measuring detector 32, in particular that they do not overlap.

Furthermore, by using the imaging optics 157 in the embodiment according to 3 the numerical aperture of the detector-side beam path can be selected to be larger so that scattered light generated on the sample surface can also be detected by measuring detector 46. This enables improved measurement accuracy.

In 5 A further embodiment 210 of a measuring device in the form of a reflectometer for measuring reflection properties of a sample is schematically illustrated. The measuring device 210 differs from the one in 3 illustrated measuring device 110 only in the configuration of the beam forming system 242 and therein in the configuration of the reflection grating 224 and the exit aperture 232. The reflection grating, which according to 5 with the The grid structure 28, designated by reference numeral 224, has only the grid structure 28 and is thus configured as a one-dimensional vertical grid.

The reflection grating 224 thus serves only as a monochromator for the incident beam 23, so that only one measuring beam 30-1 is generated. The exit aperture, which is in 5 is provided with the reference number 232, is therefore provided with only one passage opening 34-1. Due to the arrangement of the imaging optics 157, as already mentioned with reference to 3 described, the numerical aperture of the detector-side beam path of the measuring radiation 47 reflected by irradiation with the measuring beam 30-1 on the surface section of the sample 11 can be selected to be relatively large, so that scattered light generated on the sample surface can also be detected by the measuring detector 46.

In 4 A further embodiment 310 of a measuring device is shown schematically, which differs from the embodiment according to 1 only differs in the design of the beam forming system, which is designated here with the reference numeral 342. In this respect, the measuring device 310 differs from the embodiment according to only the section arranged in the airtight chamber 60 1 . Therefore, in 4 only the airtight chamber 60 is shown, analogous to the 1 in side view. The section arranged in the airtight chamber 60 differs only in the configuration of the outlet aperture, which is 4 designated by the reference numeral 332.

The exit aperture 332 has only one passage opening 34-1. Furthermore, the exit aperture 332 is arranged on a corresponding bearing 333 so as to be displaceable in the y-direction, ie transverse to the measuring beams 30-1 and 30-2. The exit aperture 332 can thus be displaced between two positions at which either the first measuring beam 30-1 or the second measuring beam 30-2 can pass through the passage opening 34-1. The optical beam shaping system 42 is thus in accordance with 4 configured to successively generate the measuring beams 30-1 and 302 directed at different locations on the sample 12.

6 shows schematically a further embodiment 410 of a measuring device in the form of a reflectometer for measuring reflection properties of a sample 12. The view in 6 is analogous to the view in 1 a side view. The measuring device 110 according to 6 differs from the measuring device 10 according to the 1 and 2 only in the configuration of the beam forming system 42, which in 3 designated by the reference numeral 442, and in this case specifically in the configuration of the reflection grating 24, the exit aperture 32 and the collecting mirror 36.

The reflection grating is in the embodiment according to 6 designated by the reference numeral 424 and differs, as does the reflection grating 224 according to 5 , from the reflection grating 24 according to 1 in that it only has the grating structure 28 and is thus configured as a one-dimensional vertical grating. The reflection grating 424 thus serves only as a monochromator for the incident beam 23, the exit aperture, which in 6 is provided with the reference number 432, is therefore, like the exit aperture 232 according to 5 , provided with only one passage opening 34-1.

The collecting mirror is in the embodiment according to 6 designated by the reference numeral 436 and differs from the collecting mirror 36 according to 1 in that it is provided with the grating structure 26 on its reflective surface and is thus configured as a one-dimensional horizontal reflection grating. The splitting of the monochromatized beam 23 into the measuring beams 30-1 and 30-2 thus only takes place in this embodiment at the collecting mirror 136. In this embodiment, this is therefore also referred to as a beam splitting module instead of the reflection grating 24. According to an alternative embodiment, instead of arranging the grating structure 26 on the collecting mirror, a Fesnel prism can be arranged in the immediate vicinity of the collecting mirror 436 and take on the function of the beam splitting module.

This means that in the 6 In the embodiment shown, the first grating structure 26 and the second grating structure 28 are arranged at different locations in the beam path of the measuring radiation 16 within the beam shaping system 442. In particular, the first grating structure 26 is arranged downstream of the second grating structure 28 in the beam path of the measuring radiation within the beam shaping system 442.

The provisions already made with reference to the embodiment according to 1 and 2 mentioned optional formation of a separate airtight chamber 62 for the collecting mirror 36 is in the embodiment according to 6 This is particularly advantageous. The collecting mirror 136 can be replaced with little effort if necessary. The recording of the measurement and reference intensities is carried out analogously to the embodiment according to the 1 and 2 by means of the measuring detector 46 and the reference detector 44.

7 shows an embodiment of a projection exposure system 80 for microlithography with a plurality of mirror elements 100, which can be used as samples for the measuring device 10, 110, 210, 310 or 410 according to the invention. The present embodiment is designed for operation in the EUV wavelength range, ie with electromagnetic radiation with a wavelength of less than 100 nm, in particular a wavelength of about 13.5 nm or about 6.8 nm. Due to this operating wavelength, all optical elements are designed as mirrors. Other embodiments of projection exposure systems are designed for operating wavelengths in the UV range, for example 365 nm, 248 nm or 193 nm. In this case, at least some of the optical elements are configured as conventional transmission lenses.

The projection exposure system 80 according to 7 comprises an exposure radiation source 82 for generating exposure radiation 84. In the present case, the exposure radiation source 82 is designed as an EUV source and can, for example, comprise a plasma radiation source. The exposure radiation 84 first passes through an illumination optics 86 and is directed by this onto a mask 88.

The mask 88 has mask structures which are imaged onto a substrate 94 in the form of a wafer during exposure operation of the projection exposure system 80, and is movably mounted on a mask displacement stage 90. The substrate 94 is movably mounted on a substrate displacement stage 96. The mask 88 can, as in 7 shown, can be designed as a reflection mask or alternatively, in particular for UV lithography, can also be configured as a transmission mask. The exposure radiation 84 is in the embodiment according to 7 reflected on the mask 88 and then passes through a projection lens 92, which is configured to image the mask structures onto the substrate 94. The substrate 94 is movably mounted on a substrate displacement stage 96. The projection exposure system 80 can be designed as a so-called scanner or as a so-called stepper. The exposure radiation 84 is guided within the illumination optics 86 and the projection lens 92 by means of a plurality of optical elements, in the present case in the form of mirrors.

In the embodiment shown, the illumination optics 86 comprise four optical elements in the form of mirror elements 100-1, 100-2, 100-3 and 100-4. The projection lens 92 also comprises four optical elements in the form of mirror elements 100-5, 100-6, 100-7 and 100-8. The mirror elements 100-1 to 100-8 are arranged in an exposure beam path 98 of the projection exposure system 80 to guide the exposure radiation 84.

Each of the mirror elements 100-1, 100-2, 100-3, 100-4, 100-5, 100-6, 100-7 and 100-8 can be measured as sample 12 in the measuring device 10 or 110, as shown in 7 indicated as an example for the mirror element 100-5.

The above description of exemplary embodiments, embodiments or variants is to be understood as exemplary. The disclosure made thereby enables the person skilled in the art to understand the present invention and the associated advantages, and on the other hand also includes obvious changes and modifications to the structures and methods described in the understanding of the person skilled in the art. Therefore, all such changes and modifications, insofar as they fall within the scope of the invention as defined in the appended claims, as well as equivalents, are intended to be covered by the protection of the claims.

List of reference symbols

10

Measuring device

11

Sample holder

12

sample

13

Pivoting bearing

14

Radiation source

16

Measuring radiation

18-1, 18-2

Measuring locations

19

Angle of incidence

20

Entrance panel

22

Collecting mirror

23

convergent beam

24

Reflection grid

25

two-dimensional grid

26

first lattice structure

28

second lattice structure

30-1, 30-2

Measuring beams

32

Exit aperture

34-1, 34-2

Passage openings

36

Collecting mirror

38

Beam splitter

40

Intermediate focus

42

Beam forming system

44

Reference detector

46

Measuring detector

47

reflected measuring radiation

48

Tiltability

50

Displaceability in y-direction

52

Displaceability in z-direction

54, 56, 58, 60, 62

airtight chambers

63

optical window

64

Access flap

66

Evaluation device

80

Projection exposure system

82

Exposure radiation source

84

Exposure radiation

86

Lighting optics

88

mask

90

Mask transfer platform

92

Projection lens

94

Substrat

96

Substrate transfer stage

98

Exposure beam path

100-1, 100-2, 100-3, 100-4, 100-5, 100-6, 100-7, 100-8

Mirror elements

110

Measuring device

147

reflected measuring radiation

157

Imaging optics

159-1, 159-2

Mirror elements

210

Measuring device

224

Reflection grid

232

Exit aperture

242

Beam forming system

310

Measuring device

332

Exit aperture

333

movable storage

342

Beam forming system

410

Measuring device

424

Reflection grid

432

Exit aperture

436

Collecting mirror

442

Beam forming system

QUOTES INCLUDED IN THE DESCRIPTION

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Cited patent literature

• US 6856395 B2 [0003]

Claims (19)

Measuring device (10; 110; 310; 410) for measuring reflection properties of a sample (12) with: - a radiation source (14) for providing a measuring radiation (16), - an optical beam shaping system (42; 142; 342; 442) which is configured to generate from the measuring radiation a plurality of measuring beams (30-1, 30-2) directed at different locations (18-1, 18-2) of the sample, and is further configured to set a wavelength of the measuring beams, and - a detector (46) for detecting radiation (147) of the measuring beams reflected on the sample. Measuring device according to Claim 1 , wherein the optical beam forming system (42; 142) is configured to generate the measuring beams (30-1, 30-2) by splitting an input beam (23) containing the measuring radiation. Measuring device according to Claim 1 or 2 which is configured for wavelength-dependent measurement of the reflection properties of the sample (12) and in which the optical beam shaping system (42; 142) is further configured to adjust a wavelength of the measuring beams (30-1, 30-2). Measuring device according to Claim 3 , wherein the beam forming system (42; 142) is configured to vary the wavelength of the measuring beams (30-1, 30-2). Measuring device according to one of the preceding claims, which further comprises an evaluation device (66) which is configured to simultaneously determine the reflection properties of the sample at the different locations (18-1, 18-2) from the reflected radiation of the measuring beams (30-1, 30-2) detected by the detector (46). Measuring device according to one of the Claims 1 until 4 , in which the optical beam shaping system (342) is configured to successively generate the measuring beams (30-1, 30-2) directed at different locations on the sample. Measuring device according to one of the Claims 1 until 4 or after Claim 6 , wherein the optical beam shaping system comprises an aperture (332) which is configured to allow at least a first of the measuring beams (30-1) to pass through and simultaneously block at least a further one of the measuring beams (30-2), wherein the aperture is displaceably mounted between at least two positions at which either the first measuring beam or the further measuring beam is allowed to pass through. Measuring device according to one of the preceding claims, wherein the optical beam shaping system (42; 142) comprises a grating structure (28) for generating the measuring beams directed to the different locations (18-1, 18-2) of the sample from the measuring radiation. Measuring device according to Claim 8 , in which the optical beam shaping system (42; 142) comprises a further grating structure (26) for adjusting the wavelength of the measuring beams. Measuring device according to Claim 9 , in which the further grid structure (26) is arranged transversely to the first grid structure (28). Measuring device according to Claim 10 , in which the first grid structure (26) and the further grid structure (28) form a two-dimensional grid (25). Measuring device according to Claim 9 or 10 , in which the first grating structure (26) and the further grating structure (28) are arranged at different locations in the beam path of the measuring radiation (16) within the beam shaping system (142). Measuring device according to one of the preceding claims, further comprising an imaging optics (157) which is arranged in a beam path of the reflected radiation (147) between the sample (12) and the detector (46). Measuring device according to one of the preceding claims, wherein the radiation source (14) is configured to generate the measuring radiation (16) in the EUV wavelength range. Measuring device according to one of the preceding claims, in which the beam shaping system (42; 142) comprises a beam splitting module (24; 136) for splitting an input beam (23) containing the measuring radiation (16) into the measuring beams (30-1, 30-2), wherein the measuring device (10; 110) further comprises a first airtight chamber (54, 56, 60) in which at least one module of the measuring device arranged in a beam path of the measuring radiation is arranged, and a further airtight chamber (58; 62) in which the beam splitting module is arranged. Measuring device according to Claim 15 , wherein the module of the measuring device arranged in the first airtight chamber (54, 56, 60) is another module (22, 36; 136) of the beam shaping system (42; 142). Measuring device according to one of the preceding claims, which is configured to measure the reflection properties of an optical element (100-5) for microlithography. Measuring device (10; 110; 210; 310; 410) for measuring reflection properties of a sample (12) with: - a radiation source (14) for providing a measuring radiation (16), - an optical beam shaping system (42; 142; 242; 342; 442), which is configured to generate at least one measuring beam (30-1; 30-2) directed at the sample from the measuring radiation, and is further configured to set a wavelength of the measuring beam, - a detector (46) for detecting radiation (147) of the measuring beams reflected on the sample, and - an imaging optics (157), which is arranged in a beam path of the reflected radiation between the sample and the detector. Method for measuring reflection properties of a sample (12) with the steps: - generating several measuring beams (30-1; 30-2) directed at different locations on the sample, - setting a wavelength of the measuring beams, and - detecting radiation (147) of the measuring beams reflected on the sample.