DE102009047180A1 - Facet mirror for use in extreme ultraviolet lithography, has facet which consists of multilayer structure, where multilayer structure is designed for reflection of electromagnetic radiation in extreme ultraviolet wavelength range - Google Patents

Abstract

The facet mirror has a facet (1) which consists of a multilayer structure (3). The multilayer structure is designed for the reflection of electromagnetic radiation in the extreme ultraviolet wavelength range. The upper surface (7) of the multilayer structure is tilted against the boundary surface (6) of the layers (4,5) of the multilayer structure. An independent claim is also included for a lighting system with a light source.

Description

The The present invention relates to a facet mirror for use in EUV lithography with at least one facet, which has a multilayer structure suitable for reflection of electromagnetic radiation in the extreme ultraviolet wavelength range is designed. Furthermore, the invention relates to lighting systems as well Projection exposure equipment operating at one wavelength operated in the extreme ultraviolet wavelength range be, with such facet mirrors.

Around in the production of semiconductor devices with lithographic Methods to be able to produce ever finer structures worked with increasingly short-wave light. Do you work in the extreme ultraviolet (EUV) wavelength range, such as in particular at wavelengths between about 5 nm and 20 nm no longer work with lenticular elements in transmission, but become illumination and projection lenses from mirror elements with reflective coatings adapted to the respective operating wavelength built on the basis of multilayer systems.

at Lighting systems for wavelengths smaller 100 nm is the problem that often the light source Such illumination systems emits radiation, the wavelengths which is outside the wavelength band for which in the illumination system or the projection exposure apparatus, in which the lighting system is used is designed. These electromagnetic radiation that is outside the working wavelength band, can lead to an unwanted exposure of the light-sensitive Object in the wafer plane of the projection exposure apparatus to lead. Besides, it can be the optical components so far as to heat that by deformation of the optical components Imaging errors arise and / or reflectivity, for example of multi-level mirrors, which are very common at wavelengths be used in the range of 5 to 20 nm, impaired becomes. To make matters worse, that multi-level mirror not only certain EUV wavelengths for which they have been optimized reflect with higher reflectivity, but often also wavelengths from about 130 nm and more. Therefore, will electromagnetic radiation from the deep ultraviolet (DUV) wavelength range (in particular about 130 nm to 330 nm) or from the ultraviolet (UV) range, the visible (VIS) and infrared (IR) areas throughout Lighting system or through the entire projection exposure system led, which can lead to incorrect exposures.

To the Filtering out or mitigating these unwanted Radiation spectral filters are used. Preference is given to Spectral filter as early as possible in the beam path used to affect the imaging properties and a high heat load as much as possible avoid. Often, the first optical component becomes a collector mirror formed, which also assumes spectral filter functions.

The WO 2005/119365 A2 describes a reflective spectral filter for the EUV wavelength range, which has a multilayer structure that is cut obliquely, so that a sawtooth or blazed grating is formed. The multiple layer structure has significantly more than a thousand absorber-spacer pairs, which makes their production very time-consuming and cost-intensive. The working wavelength at which EUV lithography is to be performed is conventionally reflected by Bragg reflection at the interfaces of the multilayer structure, while the EUV radiation in adjacent waves is absorbed by the multilayer structure. Wavelengths in the UV, VIS and IR ranges, on the other hand, are reflected specularly on the slants and thus deflected out of the beam path.

In the JP 06-027297 A It is proposed to obliquely cut a reflective spectrum filter for the soft X-ray wavelength range on the basis of a multi-layer structure. In this case, the intersecting angle is selected so that when grazing incidence near the critical angle for total reflection, the angle of the incident beam to the cut surface is greater than the angle of the incident beam to the interfaces of the layers of the multilayer structure. As a result, the scattered radiation and the reflection of radiation at a different angle of incidence are suppressed to reflect only a narrow wavelength band.

One category of projection exposure equipment commonly used in EUV lithography is the US 7,091,505 B2 described. This is a projection exposure apparatus which is operated in a scanning mode along a scanning direction with a wavelength in the EUV range.

Facettenspiegel are among others from the EP 0 955 641 A1 known. Frequently, two facet mirrors are provided in projection exposure equipment for EUV lithography, one of which serves as a field facet mirror, with the aid of which a plurality of images of the radiation source of the projection exposure apparatus are projected into a pupil plane in which a second facet mirror is arranged, which serves as a pupil facet mirror and superimposed on the images of the facets of the first facet mirror in the mask or reticle plane in order to allow the most homogeneous possible illumination. By the particular arrangement of the individual Different facets of the facet mirrors can be set to different illumination geometries, for example the illumination of a rectangle or a ring or ring segment or similar. The illuminated structure of the mask or of the reticle can then be projected onto a wafer to be exposed.

A Object of the present invention is the already known optical elements for filtering electromagnetic radiation, in particular for use in EUV lithography, to further develop.

These Task is solved by a facet mirror for use in EUV lithography with at least one facet, which has a multilayer structure suitable for reflection of electromagnetic radiation in the extreme ultraviolet wavelength range is designed, dissolved, the surface of the Multi - layer structure against the interfaces of the layers of the Multi-layer structure is tilted.

It It has been found that the design of facets of a Facet mirror as a mirror with spectral filter effect a number of benefits. For one thing, especially in the Design as field facet mirror the incident beam fanned out so that the thermal load, the on every single facet caused by the impinging mischief is distributed to the individual facets, so the heat load is smaller on every single facet. Be under misdirection understood all wavelengths that are not in the respective Working wavelength band of the projection exposure apparatus in the EUV area. Particularly disturbing wavelength ranges are about the wavelengths between 100 and 400 nm. If as a radiation source, a plasma source should be used, which is excited by an infrared laser, can also disturbing parts of higher intensity in the infrared wavelength range added. In exposure systems of EUV projection exposure systems can measure the distances between individual optical components, in particular the mirrors are on the order of 1 m, and already very small angles are enough to help with the proposed Facet mirrors to the next optical element a sufficient spectral separation between the working wavelength in the EUV sector and in the fraction of non-corrosive substances, in particular in the wavelength range from 100 to 400 nm. That makes a production of single mirror facets possible by simple polishing. In particular, the number of layers of the multilayer structure only needs by a small number compared to the multilayer structure of conventional mirror facet the surface parallel to the interfaces of the Layers of the multi-layer structure or to the surface of the substrate, on which the multi-layer structure is applied runs. A particular advantage is that at the individual mirror facets no stray light is created because there are no diffractive structures.

facet mirror with the facets described here, both as field facet mirrors as well as a pupil facet mirror.

Preferably All facets of the facet mirror have a multiple layer structure on that for the reflection of electromagnetic radiation are designed in the extreme ultraviolet wavelength range, the surfaces of all multilayer structures are against the Boundaries of the layers of the multilayer structure are tilted. This allows optimal use of the spectral filter function in Connection can be achieved with the advantages mentioned.

In preferred embodiments are the surface the multilayer structure and / or the interfaces of the Layers of the multilayer structure curved. The curvature can be arbitrary and can be connected to additional optical Facet mirror requirements such as focusing effect, correction be adjusted by aberrations, etc. A possibility, curved interfaces of the layers of the multilayer structure For example, it is the surface a substrate to which the multilayer structure is applied, to be provided with a corresponding curvature.

Prefers are the surface of the multilayer structure and the interfaces the layers of the multi-layer structure formed spherically. Spherical surfaces are particularly easy by polishing and also have a focusing effect.

In Particularly preferred embodiments is the Obefläche the multilayer structure as two or more tilted against each other Part surfaces formed. This has the advantage that the False light in the incident beam at each face is split into a sub-beam, the one to another Body distracted and then by different action such as apertures, light traps or additional optical elements can be taken out of the beam. Especially Preferably, the surface of the multi-layer structure is as two mutually tilted spherical surfaces educated. This can be done by simply polishing produce and lead without much effort to a focusing effect.

In a further aspect, this object is achieved by an illumination system for a projection exposure apparatus which operates with a wavelength in the extreme ultraviolet wavelength range ben, and has a facet mirror as already described. The spectral filtering in the illumination system of an EUV projection exposure apparatus, in particular by a field facet mirror and / or a pupil facet mirror, has the particular advantage that the modification of the mirror facets, in order to give them the function of a spectral filter, usually only leads to defocusing or the drift of a Focus leads, which can be corrected with relatively little effort. Assuming the spectral filtering in the projection system, it can lead to wavefront aberrations, which are more complex to correct.

In preferred embodiments is the facet mirror with the facets described above formed as a field facet mirror and a pupil facet mirror is provided in addition to a light source, on the field facet mirror emitted from the light source radiation with the pupil facet mirror having one or more light traps. The light traps are preferably on the pupil facet mirror located where the single beam of each field facet mirror after spectral separation from the working wavelength band in the EUV area. The light traps can be formed arbitrarily. For example, this may be highly absorbing layers act, which impinges the incidental light absorb to a great extent. It can be recesses acting in the pupil facet mirror, through which passes the stray light and so that the system leaves. The light traps can be formed as a hollow body in which the stray light almost expires. The light traps can also be called Apertures may be formed in their shape to the distribution of False light rays and EUV rays are adapted such that only the false light rays are hidden. Especially Preferably, the pupil facets are arranged such that the False light rays through the spaces between the passes through individual pupil facets. Advantageously stand the light traps in thermal contact with a cooling system to be able to dissipate the thermal power of the stray light. The cooling system of the pupil facet mirror is preferred used, if one exists. As beneficial it has also been found in one or more light traps one or more provide multiple sensors, for example, to measure the radiation intensity.

In a further preferred embodiment of the illumination system is also the facet mirror with the facets described above as Field facet mirror formed and are a light source and a Pupillenfacettenspiegel provided on the field facet mirror Radiation emitted by the light source, wherein the pupil mirror having one or more mirrors oriented in such a way that radiation reflects back towards the light source can be. Advantageously, these mirrors are used to reflect false light back towards the light source, while the EUV radiation, especially in the working wavelength band in a conventional manner on the individual pupil facets is directed towards the reticle or mask. By use of mirrors to direct the stray light out of the beam path, will allow that misleading into previously unused Steer corners of the lighting system, which also larger dimensioned light traps or associated cooling systems installed without the visual function of the lighting system disturb. Particularly preferred are the mirrors for the reflection of infrared light is used. Preferably the at least one mirror has a metal surface, an aluminum surface, a silicon surface or a highly reflective layer system.

It It should be noted that the facet mirror with the above Facets may be formed as a pupil facet mirror, wherein light traps or deflecting mirror on one of the optical path following in the beam path Elements of the lighting system can be arranged or also on the reticle or the mask itself.

In In another aspect, the object is achieved by a projection exposure apparatus solved that with a wavelength in the extreme ultraviolet Wavelength range is operated and the one as before having a facet mirror as described, and by a projection exposure apparatus, those with a wavelength in the extreme ultraviolet wavelength range operated, which is a lighting system as described above having.

The The foregoing and other features are excluded from the claims also from the description and the drawings, the individual Characteristics in each case alone or in several form sub-combinations in one embodiment of the invention and be realized and advantageous in other fields as well represent protectable versions can.

The The present invention is intended to be better understood with reference to a preferred Embodiment will be explained in more detail. Show this

1 schematically a first variant of a facet of a facet mirror;

2 schematically a second variant of a facet of a facet mirror;

3 schematically an embodiment ei nes lighting system;

4 schematically a projection exposure system for EUV lithography;

5a , b schematically shows an arrangement of field facets of a first embodiment in conjunction with an arrangement of pupil facets;

5c , d diaphragms for use with the arrangements of 5a , b;

6a Fig. 2 schematically shows an arrangement of field facets of a second embodiment in conjunction with an arrangement of pupil facets;

7a schematically a pupil facet arrangement in plan view;

7b c schematically shows two variants of a pupil arrangement as in FIG 7a on average with light trap;

8a schematically another embodiment of a lighting system; and

8b schematically a section through a part of the pupil facet mirror of the illumination system 8a ,

In 1 is schematically a first variant of a facet 1 a facet mirror, which is a multilayer structure 3 has, whose surface 7 against the interfaces 6 the layers 4 . 5 the multi-day structure 3 is tilted. In the multi-layer structure 3 These are essentially layers of a material which is somewhat more absorbent at the desired operating wavelength, and also absorbers 4 called, and a little less absorbent material, also spacers 5 called. About these alternating layers 4 . 5 a crystal is simulated, with the absorber layers 4 correspond to the lattice planes at which Bragg reflection can take place. The thickness of a stack of absorber layer 4 and spacer layer 5 Can over the whole multi-day system 3 be constant or variable. There may also be additional layers between absorber 4 and spacers 5 be provided. The first layer on the substrate 2 can be an absorber layer 4 or a spacer layer 5 be. Also, the final vacuum towards the position can both an absorber layer 4 as well as a spacer layer 5 be. Both between substrate 2 and multi-day system 3 as well as on the multi-day system 3 towards the vacuum, one or more additional layers may be provided.

In a multi-layered structure 3 for example, molybdenum as an absorber and silicon as a spacer for reflection of EUV light 8th At a wavelength of about 13.5 nm, the stack of absorber and spacer has a thickness d of about 7 nm. As a rule, the EUV radiation penetrates 8th into about fifty stacks and is reflected at each molybdenum-silicon interface. Constructive interference of the individual reflections in the far field produces an EUV reflex with a reflectivity of more than 50%. Since the refractive index is almost identical to 1 for both silicon and molybdenum, a tapered surface is used 7 with wedge angle α as in 1 barely showed a change in direction of the reflected EUV beam 8th , At a wedge angle α of 1 mrad the direction change is only 60 μrad. The false light background with wavelengths of more than about 50 nm no longer dissolves the multilayer structure on the order of 7 nm, so that only a reflective reflection on the surface can take place to the vacuum. However, according to the geometric optics, the angle of incidence is equal to the angle of reflection. At a wedge angle α of 1 mrad thus results in a change in direction of the false light beam 9 at 2 mrad. It is therefore larger by a factor of 30 than in the EUV beam 8th , This results in that at a distance of 1 m EUV beam 8th and false light beam 9 already separated by 2 mm from each other.

In 2 is another variant of one with a multi-day system 3 provided facet 1 a facet mirror shown. Unlike the in 1 variant shown are both the surface of the substrate 2 on which the multilayer structure 3 is applied, as well as the trimmed surface 7 the multi-day structure 3 formed curved. Both in the in 1 variant shown as well as in the 2 variant shown run the interfaces 6 between the individual layers 4 . 5 the multi-day structure 3 parallel to the surface of the substrate 2 , Depending on the requirements of the optical properties or the spectral effect of the multi-layer structure 3 or the facet 1 can the interfaces 6 and the surface of the substrate 2 also have different courses. In the embodiment with curved surfaces such as in 2 shown, the curvature curves of the interfaces 6 as well as the surface 7 be arbitrary. In the example in 2 variant shown have both the surface 7 as well as the interface 6 a substantially spherical course. This led to a focusing effect of the facet 1 , The EUV beam 8th who is in the multi-day structure 3 at the individual interfaces 6 Bragg-reflected becomes the focus 10 focused. The false light beam 9 that at the surface 7 the facet 1 Reflecting reflection becomes the focus 11 focused. A focusing effect would also be achievable, for example, in elliptical or similar processes. In the in 2 Example shown have the curvature of the surface 7 and the curvatures of the interfaces 6 essentially the same radius of curvature, so that the foci 10 and 11 essentially located in one plane. Depending on the way in which the misleading 9 should be removed from the system, it may also be useful over different radii of curvature, the EUV radiation 8th and the wrong-way 9 to focus in different levels.

In 3 schematically is an embodiment of a lighting system 20 which may be part of a projection exposure apparatus for EUV lithography. A collector mirror 23 is arranged around a light source, that of a plasma droplet 22 is formed by an infrared laser 21 is stimulated. In order to obtain high radiation intensities in the range of, for example, 13.5 nm in the EUV wavelength range, z. B. tin are excited by means of a working at a wavelength of 10.6 microns infrared laser to a plasma. In addition to the radiation in the EUV wavelength range, the plasma also emits long-wave radiation, for example in the UV wavelength range, in particular in the DUV wavelength range. About the infrared laser 21 In addition, infrared radiation is introduced into the system to a greater extent. On the collector 23 follow a field facet mirror 24 with individual field facets 12 and a pupil facet mirror 25 with individual pupil facets 13 With. Before the radiation on a reticle 28 With a structure to be projected onto a wafer, it still becomes a folding mirror 27 diverted. Im in 8th The example shown is the reticle 28 Scanned in the y-direction to project its structure onto a wafer. The folding mirror 27 has less visual function, but rather serves the space requirements of the lighting system 20 to optimize.

The beam 26 in the lighting system 20 meets the individual field facets 12 of the field facet mirror 24 , Every field facet 12 is with a multi-tier structure 3 equipped for the reflection of EUV radiation, wherein the surface of the multilayer structure is tilted against interfaces of the layers of the multilayer structure, as in connection with the 1 and 2 explained. As already explained, it takes on the facets 12 of the field facet mirror 24 a spectral separation of the incident beam 26 into an EUV beam 8th with a narrow wave band around the working wavelength and in a false beam 9 instead, whose radiation has wavelengths in the UV range and above. If, for example, the multilayer structure is a multilayer system with molybdenum as absorber and silicon as spacer and a stack thickness d of 7 nm for working wavelengths around 13.4 nm, this structure is not resolved already from wavelengths of about 50 nm, so that only another reflection on the tilted surface 7 can take place. If the angle .alpha. Between the course of the boundary surfaces between the layers of the multilayer structure and the surface tilted against it is, for example, 1 mrad, the result is a directional change of the stray light beam of 2 mrad, while the change in direction of the UV beam 8th only at 60 μrad. At a distance of one meter so are the EUV beam 8th and the stray beam 9 already 2 mm apart from each other. Im in 3 illustrated example 1 of the lighting system 20 is at this distance the pupil facet mirror 25 arranged, wherein the pupil facets 13 are dimensioned and arranged such that the of the respective field facets 12 reflected EUV radiation 8th on the corresponding pupil facet 13 occurs while the misdirected light 9 essentially in the space between two facets 13 is steered and thus removed from the system. At the pupil facet mirror 25 This will primarily only the EUV beam 8th to the reticle 28 further directed.

In 4 is a principle view of a projection exposure system 100 for the fabrication of, for example, microelectronic devices operating in a scan mode along a scan direction 116 operated at a working wavelength in the EUV range and which may have one or more facet mirrors with spectral filter function.

In the 4 shown projection exposure system 100 includes a light source 31 , as well as a collector 30 for illuminating a reticle 114 with the help of the plane mirror 300 in the beam path between the collector 30 and the intermediate focus Z. The plane mirror 300 serves to fold the system to provide installation space for mechanical and electronic components in the object plane in which the Retikelhalterung is arranged. The lighting system is followed by a field facet mirror 102 and a pupil facet mirror 104 , wherein in the example shown here, the field facet mirror 102 one or more facets may have, for example, in connection with the 1 and 2 have been described. The subsequently arranged mirrors 106 . 108 and 110 essentially serve to shape the field in the object plane. In the object plane is a structured reticle 114 arranged whose structure by means of a projection lens with six mirrors in the present example 128.1 -6 to the object to be exposed 124 , about a wafer is imaged.

The reticle 114 is in the projection exposure system designed here as a scanning system 100 in the direction shown 116 movable and is successively illuminated in sections to the respective structures of the reticle 114 with the projection lens on for example, a wafer 124 to project. The exit pupil of the illumination system is largely homogeneously illuminated and coincides with the entrance pupil of the subsequent projection objective. Have the facets of facet mirrors 102 . 104 , in particular the facets of the field facet mirror 102 an oblong shape, they are preferably arranged with the shorter side in the direction that the scanning direction 116 on the reticle 114 corresponds to a homogeneous illumination of the reticle 114 to allow.

5a shows a side view of three field facets 12 a field facet mirror. In the present example, the field facets are formed as elongated circular arc segments. In the view in 5a they are shown along their short facet side. The short facet sides are arranged along the direction y, which corresponds to the scanning direction on the reticle, in order to achieve the most homogeneous possible illumination of the reticle. Also, the tilt of the interfaces 6 the layers of the multi-layer structure 3 opposite the surface 7 the multi-day structure 3 by the angle α runs along the direction y. The field facets 12 For example, they can be prepared by first forming a spherical surface in the substrate in a polishing process 2 is polished in, then with the individual layers of the multi-layer structure 3 is coated. Subsequently, into the surface of the multi-layer structure 3 also polished in a spherical surface, which, however, opposite to the in the substrate 2 polished in spherical surface is slightly tilted. The tilt angle α is preferably in the mrad range. Im in 5a As shown, polishing bodies with the same radius were used for the polishing processes.

The different impact points of the split beams are in 5b shown in the supervision of the pupil facets 13 represents a pupil facet mirror arranged subsequent to the field facet mirror. This will be the EUV-rays 8th from the field facets 12 on foci 10 here essentially centered on the individual pupil facets 13 focused while the stray light rays 9 on foci 11 at the interstices of the pupil facets 13 be focused. By tilting the interfaces 6 the multilayer structure and the surface 7 the multi-day structure 3 in the direction y, the spectral separation in the y direction, which corresponds to the scanning direction on the reticle, also takes place. At the points of impact 11 of the plain light 9 are in the 5b illustrated example light traps 41 educated. At the light traps 41 For example, these may be recesses in the pupil facets 13 act, to which, for example, join a hollow body in which the stray light can virtually leak. For this purpose, the inner surface of the hollow body may additionally be provided with a coating which has particularly high absorption coefficients in the region of the prevailing wavelengths of the stray light. Behind the recesses 41 or the adjoining hollow bodies, a cooling system may be arranged to receive the heat load generated by the stray light. The light traps 41 may also be formed as a surface highly absorbent for the false light, which are advantageously in thermal contact with a cooling system.

Furthermore, the removal of the stray light in the region of the pupil facet mirror can also be carried out via diaphragms. Two exemplary diaphragm configurations are in the 5c and 5d shown. In the in 5c configuration shown is a contiguous aperture 46 with recesses 47 which are placed where the EUV light is to pass through the aperture. At the in 5d The configuration shown, however, are individual panel parts 49 located where the misdirected light hits. The panel parts 49 are by connecting elements to a diaphragm arrangement 48 connected with each other. The connecting elements between the panel parts 49 should be chosen so that the individual panel parts 49 be sufficiently fixed, but at the same time as little EUV light is shadowed. In particular, the connecting elements can also be curved and can, for example, run around the pupil facets in order to shade as little as possible EUV light. About the fasteners, the panel parts 49 also be brought into thermal contact with a cooling. Likewise, the aperture 46 to be in thermal contact with a cooling. Both the aperture 46 as well as the aperture parts 49 can be coated. The coating can be, for example, a coating that absorbs the single-layered coating, or it can also be a coating that is highly reflective of the single-layered coating and reflects the stray light back toward the light source.

In 6a is a variant of in 5a seen embodiment. The two variants differ in that in the facets 12 according to 6a no longer a spherical surface 7 into the multi-day structure 3 was introduced, but two faces 14 and 15 , each by angles β and γ against the course of the interfaces 6 the layers of the multi-layer structure 3 on the substrate 2 are tilted. The angles β and γ may be the same or different. Likewise, the surfaces can 14 and 15 have a similar curvature or not. In other variants, more than two partial surfaces can be provided. Im in 6a example shown is both in the partial area 14 as well as at the subarea 15 around spherical faces, each to a focus 11 of the stray light in the plane of the pupil facets 13 lead, so that on a field facet 12 incident false light is split into two beams. Every facet 12 leads to a focal point 11 above the EUV focal point 10 and another false-focus 11 below the EUV focal point 10 , As in the 5d Example shown are the pupil facets 13 again arranged so that the EUV beam of each associated field facet 12 on the respective pupil facet 13 occurs and the stray light rays are directed substantially to the spaces between the pupil facets. The spaces are again as light traps 41 educated.

Possible embodiments of the light traps 41 are exemplary in more detail in 7a to c shown. For this purpose, the pupil facet arrangement is made 7a in the 7b respectively. 7c shown in section. For better clarity, only one light trap is on average in each case 41 shown. In the in 7b illustrated variant of a light trap 41 this is formed as a recess through which the stray light 9 passes through while the EUV rays 8th on individual pupil facets 13 be reflected. The light trap designed as a recess 41 passing mischief 9 can be used inter alia for metrological purposes. For example, in the light traps 41 Sensors are arranged, which measure the radiation intensity of the stray light. Since this is proportional to the EUV intensity, in particular the operating wavelength, the current EUV intensity can be monitored in this way after a corresponding calibration.

In the in 7c illustrated embodiment that is due to the light trap 41 passing mischief 9 on the cooling 43 that by the stray light 9 caused to absorb heat load. The cooling 43 is essentially designed as a cooling plate and also serves to cool the pupil facets 13 passing over the pupil facet holder 42 with the cooling 43 to be in thermal contact.

In the in the 8a and b illustrated embodiment, the false light 9 not by light traps from the lighting system 20 but with the help of mirrors that reflect the stray light back towards the light source. For the sake of clarity, only a false-light mirror 44 shown. The number of false-vision mirrors may be arbitrary to the configuration of the facet mirrors 24 . 25 or the lighting system 20 be adjusted. In the 8a illustrated variant of the lighting system 20 is different from the one in 3 illustrated illumination system in that in the interstices of the pupil facets 13 now false-light mirror 44 are arranged, the the misleading 9 back in the direction light source on the light trap 45 to steer. The light trap 45 may in turn be formed as a recess and / or absorbent surface or the like. In particular, in the region of the light trap 45 via sensors the false light 9 be used for metrological purposes. Advantageously, the light trap 45 connected with a cooling as well as the Falschichtspiegel 44 over the pupil facets 13 and their holders 42 with the cooling 43 of the pupil facet mirror 25 can see in connection.

The use of false light mirrors is particularly recommended for filtering out radiation in the infrared range. By reflecting the infrared portion of the stray light into unused corners of the illumination system, it is possible to accommodate larger and more efficient cooling systems for receiving the heat load generated by the infrared fraction. As a mischief mirror 44 can metal surfaces, for. As aluminum or silver, serve or silicon surfaces, as well as silicon in the UV, visible and infrared band reflects well. Likewise, substrates equipped with a highly reflective layer can be used. These are particularly suitable for stray light in the wavelength band 120 up to 400 nm or wavelengths in the infrared range. It should be noted that the Falschichtspiegel 44 can be designed as a plane mirror or curved mirrors. In particular, they can have a spherical curvature in order to focus the stray light as it is reflected.

In the in the 5 to 8th In the examples shown, the focal points of the EUV radiation or of the stray light or the cross section of the corresponding ray bundles were shown as round. But they can have any shape. Furthermore, the pupil facets may also have a curved or spherical surface in order to achieve a focusing effect.

It should also be noted that in the present examples the facets of the field facet mirror have been described with multilayer structures with a cut surface. It is also possible to use such facets on the pupil facet mirror and to carry out the removal of the stray light on subsequent optical components or on the reticle. When designing appropriate illumination systems or projection exposure systems, it should then be taken into account that the heat load on the pupil facet mirror has slightly greater effects, since the angular tolerance at the pupil facet mirror is generally lower than at the field facet mirror. If the spectral separation is performed only on the pupil facet mirror, but the heat load on Pupillenfa Cette mirror on the individual pupil facets larger than when it is already performed at the field facet mirror.

The Advantages of the here presented facet mirrors, especially in the Frame of a lighting system or a projection exposure system for the EUV lithography are that no additional Scattered light is generated because no diffractive structures are used become. Furthermore, the production is already common used polishing methods possible. In particular, the production This simplifies that even the smallest tilt angle in the mrad range sufficient to achieve the effects shown here. This has the additional advantage that in the multi-layer structures on the individual facets only a few additional layers to Training the tilted surface be kept have to. This can save the effort and costs for manufacturing field facets additionally in Be held in a frame.

1

facet

2

substratum

3

Multilayer structure

4

absorber

5

spacer

6

interface

7

surface

8th

EUV beam

9

False light beam

10

EUV Focus

11

False light focus

12

field facet

13

pupil

14

first subarea

15

second subarea

20

lighting system

21

infrared laser beam

22

plasma

23

collector

24

Field facet mirror

25

Pupil facet mirror

26

beam

27

folding mirror

28

reticle

30

collector

31

light source

41

light trap

42

facets bracket

43

cooling

44

False light mirror

45

light trap

46

cover

47

recess

48

diaphragm arrangement

49

visor part

100

Projection exposure system

102

Field facet mirror

104

Pupil facet mirror

106

mirror

108

mirror

110

mirror

114

reticle

124

wafer

126

projection lens

126.1-6

mirror

300

plane mirror

d

stack thickness

α, β, γ

tilt angle

y

scanning direction

Z

intermediate focus

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 2005/119365 A2 [0005]
• - JP 06-027297 A [0006]
• - US 7091505 B2 [0007]
• EP 0955641 A1 [0008]

Claims (14)

Facet mirror for use in EUV lithography with at least one facet ( 1 ), which has a multilayer structure ( 3 ) suitable for the reflection of electromagnetic radiation ( 8th ) is designed in the extreme ultraviolet wavelength range, wherein the surface ( 7 ) of the multilayer structure against the interfaces ( 6 ) of the layers ( 4 . 5 ) of the multilayer structure ( 3 ) is tilted. Facet mirror according to claim 1, characterized in that all facets ( 1 ) a multilayer structure ( 3 ) suitable for the reflection of electromagnetic radiation ( 8th ) in the extreme ultraviolet wavelength range, wherein the surface ( 7 ) of the multilayer structure against the interfaces ( 6 ) of the layers ( 4 . 5 ) of the multilayer structure ( 3 ) are tilted. Facet mirror according to claim 1 or 2, characterized in that the surface ( 7 ) of the multilayer structure ( 3 ) and / or the interfaces ( 6 ) of the layers ( 4 . 5 ) of the multilayer structure ( 3 ) are curved. Facet mirror according to one of claims 1 to 3, characterized in that the surface ( 7 ) of the multilayer structure ( 3 ) and the interfaces ( 6 ) of the layers ( 4 . 5 ) of the multilayer structure ( 3 ) are spherically formed. Facet mirror according to one of claims 1 to 4, characterized in that the surface ( 7 ) of the multilayer structure ( 3 ) as two or more mutually tilted faces ( 14 . 15 ) is trained. Facet mirror according to claim 5, characterized in that the surface ( 7 ) of the multilayer structure ( 3 ) as two mutually tilted spherical surfaces ( 14 . 15 ) is trained. Illumination system for a projection exposure apparatus operating at a wavelength in the extreme ultraviolet wavelength range, with a facet mirror ( 24 . 25 . 102 . 104 ) according to one of claims 1 to 6. Illumination system according to claim 7, wherein the facet mirror is referred to as field facet mirror ( 24 . 102 ) is formed with a light source ( 31 . 22 ) and a pupil facet mirror ( 25 . 104 ) to which the field facet mirror ( 24 . 102 ) from the light source ( 31 . 22 ) emitted radiation ( 26 ), characterized in that the pupil facet mirror ( 25 . 104 ) one or more mirrors ( 44 ) aligned such that radiation ( 9 ) back towards the light source ( 22 . 31 ) can be reflected. Illumination system according to claim 7 or 8, characterized in that the at least one mirror ( 44 ) has a metal surface, an aluminum surface, a silicon surface or a highly reflective layer system. Lighting system according to one of claims 7 to 9, wherein the facet mirror as a field facet mirror ( 24 . 102 ) is formed with a light source ( 31 . 22 ) and a pupil facet mirror ( 25 . 104 ) to which the field facet mirror ( 24 . 102 ) from the light source ( 31 . 22 ) emitted radiation ( 26 ), characterized in that the pupil facet mirror ( 25 . 104 ) one or more light traps ( 41 . 45 . 46 . 48 ) having. Illumination system according to claim 10, characterized in that the at least one light trap is used as a diaphragm ( 46 . 48 . 49 ) and / or absorbent layer and / or hollow body ( 41 ) is trained. Lighting system according to claim 10 or 11, characterized characterized in that in the at least one light trap, a sensor is arranged. Projection exposure apparatus operating at a wavelength in the extreme ultraviolet wavelength range with a facet mirror ( 24 . 25 . 102 . 104 ) according to one of claims 1 to 6. Projection exposure apparatus operating at a wavelength in the extreme ultraviolet wavelength range with a lighting system ( 20 ) according to one of claims 7 to 12.