DE102016206202A1 - Optical assembly with a rinsing device and optical arrangement with it - Google Patents

Abstract

The invention relates to an optical assembly (31) comprising: an optical element (13) having a plurality of individual mirrors (13a, 13b, ...) mounted on a common support structure (17), the individual mirrors (13a, 13 b, ...) in each case have a mirror body (19 a, 19 b,...) Whose first side (21 a, 21 b..., Facing away from the support structure (17) forms a reflecting surface, and with a plurality of actuators for Displacement, in particular for tilting, the mirror body (19a, 19b, ...) of a respective individual mirror (13a, 13b, ...) relative to the support structure (17). The optical assembly (31) has a purging device (25) for generating a purging gas stream (26), which is defined by a gap (24a, ...) between the mirror bodies (19a, 19b, ...) of at least two adjacent individual mirrors ( 13a, 13b, ...), wherein the purge gas stream (26) from one of the support structure (17) facing the second side (22a, 22b, ...) of the mirror body (19a, 19b, ...) in the direction of the first side (21a, 21b, ...) of the mirror body (19a, 19b, ...) is aligned. The invention also relates to an optical arrangement, in particular an EUV lithography system, with at least one such optical assembly (31).

Description

Background of the invention

The invention relates to an optical assembly, comprising: an optical element having a plurality of individual mirrors, which are mounted on a common support structure, wherein the individual mirrors each have a mirror body whose first side facing away from the support structure forms a reflective surface, and with a plurality of Actuators for the displacement, in particular for tilting, the mirror body of a respective individual mirror relative to the support structure. The invention also relates to an optical arrangement, for example an EUV lithography system, with at least one such optical assembly.

For the purposes of this application, an EUV lithography system is understood to mean an optical system or an optical arrangement for EUV lithography, i. an optical system that can be used in the field of EUV lithography. In addition to an EUV lithography system, which is used for the production of semiconductor devices, the optical system can be, for example, an inspection system for inspecting a photomask used in an EUV lithography system (also referred to below as a reticle) for inspecting a semiconductor substrate to be patterned (described in US Pat Hereinafter also referred to as wafers) or a metrology system which is used for measuring an EUV lithography system or parts thereof, for example for measuring a projection system.

When using EUV radiation at wavelengths in the range between about 5 nm and about 30 nm, for example, in EUV lithography systems, the contamination of optical elements by contaminating substances is a particular problem. Contaminating substances can be generated for example in an EUV light source in which a target material, for example in the form of tin droplets, is used to generate the EUV radiation. The target material in the form of the tin droplets can be converted into a plasma state by means of a laser beam, as a result of which the tin droplets partially evaporate and tin particles are formed. The tin particles can spread in the EUV lithography system and attach either directly or in the form of a tin layer on the optical surface of optical elements, for example in the illumination system or in the projection system as well as mechanical or mechatronic components of the EUV lithography.

The contamination of the surfaces by tin particles can be done in different ways: The tin particles can be deposited directly from the gas phase on the optical surfaces or a tin layer can be formed by a surface diffusion of tin. Tin contaminations may also be due to outgassing effects on tin-containing components in the EUV lithography equipment caused by hydrogen present in the EUV lithography equipment or a hydrogen plasma. The deposition of tin on the optical surfaces of the optical elements can also lead to the formation of bubbles in a reflective coating of the optical elements, which in the worst case results in delamination of the coating. Even mechatronic components can be severely limited in their function by penetrating tin particles and possibly destroyed.

The mechatronic components may, for example, be individual mirrors in the form of micromirrors which can be actuated and which are therefore also referred to as MEMS ("microelectromechanical system") mirrors. Such individual mirrors may be mounted on a common support structure (a substrate) and their mirror bodies having a reflective surface may form the facet elements of a facet mirror. The facet elements of the facet mirror are usually arranged in a grid and can be displaced individually relative to the support structure, typically tilted relative to the support structure. Such facet mirrors can be used for example in an illumination system of an EUV lithography system. It should be understood that such a facet mirror may also include conventional (i.e., macroscopically) sized individual mirrors.

In order to keep away tin particles and other contaminants from the surfaces of optical elements, such as faceted mirrors, various measures are known:
From the US 2010/0195076 A1 For example, an optical membrane element for a lithography device has been disclosed which has at least one membrane layer and a frame which at least partially surrounds the at least one membrane layer and to which at least a part of the edge of the membrane layer is attached. It is provided at least one clamping element to clamp the membrane adjustable. The membrane element can be arranged in an EUV lithography system, for example in front of a mirror of an illumination system.

In the DE 10 2012 213 927 A1 an EUV lithography system is described with a device for generating a gas curtain for redirecting contaminants. Of the Gas curtain may in particular be formed at an opening between two vacuum chambers of the EUV lithography system, for example at an intermediate focus to prevent the passage of contaminants from one vacuum chamber into the other vacuum chamber. In the region of the opening, a tubular housing can be provided. To create the gas curtain, a gas nozzle can open into the tubular enclosure.

Object of the invention

The object of the invention is to provide an optical assembly and an optical arrangement, in particular an EUV lithography system, with at least one such optical assembly in which an optical element with a plurality of individual mirrors, in particular a faceted mirror, effectively protects against contaminating substances can be.

Subject of the invention

This object is achieved by an optical assembly of the type mentioned, which has a purging device for generating a purge gas stream passing through a gap between the mirror bodies of at least two adjacent individual mirrors, wherein the purge gas stream from one of the support structure facing the second side of the mirror body in the direction is aligned with the first side of the mirror body, on which the respective reflective surface is formed.

According to the invention, it is proposed to guide a purging gas flow through the gaps between the actuatable mirror bodies of adjacent individual mirrors, which extends from the second side (the rear side) through the gap to the first side (the front side) of a respective mirror body. In this case, use is made of the fact that a gap or a distance between the mirror bodies of adjacent individual mirrors is present for the displacement, in particular the tilt, of the typically substantially plate-shaped mirror body, relative to the support structure, through which the purge gas flow can pass.

It has proved to be advantageous if the purge gas stream passes through all the gaps formed between mutually adjacent individual mirrors of the optical element. Optionally, however, the purging device may be configured to guide the purge gas flow only through gaps extending between the mirror bodies of two adjacent groups of individual mirrors. In the case of a faceted mirror, it is possible for there to be a plurality of groups of individual mirrors in each of which a specific number of facet elements are combined, for example a number of 5 × 5 facet elements. The distance and hence the width of the gap between adjacent individual mirrors of such a group is usually less than the distance or the width of a gap between the individual mirrors of a first group and an adjacent second group of individual mirrors. It is understood that the gaps in a regular arrangement of the individual mirrors e.g. extend in a grid both in the longitudinal direction and in the transverse direction and also the purge gas flow has corresponding partial flows, which are guided by the longitudinally extending or transversely extending spade.

If the purge gas stream, which exits through the gaps on the front side of the individual mirrors or of the optical element, has sufficient strength, then penetration of contaminating substances, in particular of molecular or possibly tin in the form of particles, can occur through the gaps in FIG a clearance formed between the mirror bodies and the support structure can be prevented. In this way, it can be prevented, in particular, that the contaminating substances, in particular in the form of particles, reduce the actuation range in which the mirror bodies can be displaced, for example tilted.

Electromagnetically operating actuators, for example Lorentz actuators, piezoactuators or reluctance actuators, are typically used as actuators for the mirror bodies of the individual mirrors, the latter being based on a change in the magnetic resistance. Conductive contaminants, such as tin, which deposit on surfaces in the gap may inadvertently alter the action of the actuators on the mirror bodies, e.g. by creating an electrostatic potential. The flushing gas flow can also prevent this undesired effect of the contaminating substances on the optical element. The purge gas stream exiting the gaps between the individual mirrors is directed away from the reflective surfaces of the individual mirrors and therefore may also serve to protect not only the interstice, but also the reflective surfaces of the mirror bodies from contaminants.

In one embodiment, the purging device has at least one outlet opening for exiting purge gas in a gap between the second side of the mirror body facing the support structure and the support structure.

In order to enable a displacement, for example a tilt, of the mirror body, the mirror bodies are spaced from the common support structure, ie there is a gap between the mirror bodies and the support structure, in which the purge gas can be supplied. For the supply of the purge gas into the gap there are different possibilities:
For example, the purge gas can be supplied via an outlet opening to the intermediate space, which is formed laterally at the intermediate space. In particular, when the gap is laterally sealed against the environment, for example by a circumferential side wall, it may be sufficient to supply the purge gas only through such a lateral outlet opening or possibly through a single formed in the support structure outlet opening in the intermediate space, since for the production a directed to the front of the mirror body flushing gas flow already a comparatively small pressure in the space is sufficient. It is therefore not absolutely necessary to generate a purge gas stream already aligned in the intermediate space between a respective gap between adjacent mirror bodies, but it may be sufficient if the purge gas in the intermediate space has a static pressure which is greater than the pressure in the environment of optical element or at the front of the mirror body.

If the optical element is designed to reflect EUV radiation, this is usually arranged in a vacuum environment. The pressure in the vicinity of the optical element, in particular on the front side of the mirror body, is therefore low, so that the generation of a slight overpressure in the intermediate space with the aid of the purge gas can take place in a comparatively simple manner. In particular, a dynamic balance may be established between the ambient pressure and the pressure in the gap leading to a substantially stationary purge gas flow from the gap to the front of the mirror bodies. To generate a desired purge gas flow, the vacuum or the static pressure in the vicinity of the optical element can be set appropriately, wherein the static pressure in the vicinity of the optical element, for example between 1 Pa and 10 Pa, preferably between 3 Pa and 8 Pa, in particular is between 4 Pa and 6 Pa.

In a further development, at least one outlet opening is aligned with a gap between two adjacent mirror bodies, i. the normal direction in the center of the exit opening is aligned with the gap. In this case, a purge gas flow is already generated in the intermediate space, which is aligned with the gap. This is particularly favorable for the case that the flushing of the entire space between the mirror bodies and the support structure would lead to a high consumption of purge gas, for example, because at the lateral edges of the gap no sufficient seal is present, so that possibly a not insignificant Proportion of the purge gas does not escape through the gaps between the individual mirrors, but laterally from the gap.

In a further development, the purging device has at least one tubular purging gas line which runs in the intermediate space parallel to a gap between adjacent mirror bodies and which has at least one outlet opening which is preferably aligned with the gap. In this development, the purge gas is passed through the tubular purge gas line and exits through the at least one outlet opening in the direction of a gap between adjacent mirror bodies. The tubular purge gas conduit is preferably located in the extension of the nip in the gap below the nip, or aligned with the nip, to facilitate the supply of purge gas to the nip and minimize purge gas consumption.

In a further development, the flushing device has at least one outlet opening, which is formed on the support structure, more precisely on the front side of the support structure facing the individual mirrors or the mirror bodies. In this case, the support structure typically has a supply line for the purge gas which runs through the support structure or opens out into the support structure. The supply line may extend from the back of the support structure facing away from the mirror bodies through the support structure, but it is also possible for a distribution chamber to be formed in the support structure, which has a plurality of outlet openings for exiting the flushing gas from the support structure into the intermediate space. Also in this case, the outlet openings may be aligned with the respective column or arranged in alignment with the columns.

In another embodiment, the purging device is configured to generate a purge gas stream containing a purge gas selected from the group comprising: hydrogen, nitrogen, and noble gases. If the individual mirrors of the optical element are designed for the reflection of EUV radiation, it is favorable if purge gases with a small molecular weight, for example hydrogen or helium, are used, since these have only a comparatively low absorption at low partial pressures for EUV radiation , In principle, however, other inert gases such as nitrogen or heavier noble gases such as argon can be used as purge gas. It is understood that the purge gas can also be formed from mixtures of the above-mentioned gases.

In a further embodiment, the flushing device comprises at least one supply line for supplying the flushing gas to the optical Element, typically to the support structure of the optical element. The purge gas is typically taken from the purge means a gas reservoir and fed via the supply line to the optical element. The optical element, to which the purge gas is supplied, is typically arranged with the reflecting surfaces of the individual mirrors in the optical path of an optical arrangement and the feed line extends outside the beam path of this optical arrangement.

In a further embodiment, the mirror body of a respective individual mirror is mounted on a columnar support element attached to the support structure. The columnar support member carries the generally substantially plate-shaped mirror body. As a rule, the pillar-shaped support element engages on the underside of the mirror body essentially centrally on the mirror body. The mirror body can be tilted by means of the actuator usually about at least one axis, which is typically aligned perpendicular to a central axis of the support body.

In a further embodiment, the width of the gap between adjacent mirror bodies is between 30 μm and 70 μm, preferably between approximately 40 μm and approximately 50 μm. In this embodiment, the individual mirrors are typically micromirrors and the optical element, on whose support structure the individual mirrors are mounted, is a so-called MEMS mirror. In the case of micromirrors, a gap with the width indicated above is generally sufficient to allow tilting of the mirror bodies relative to the support structure. The width of the gap is in this case measured in a basic position of the individual mirrors, in which they are not deflected with the aid of the actuators and are generally aligned parallel or substantially parallel to each other, so that a respective gap has a substantially constant width.

In one embodiment, the distance between the first side of the mirror body and the support structure is between 500 .mu.m and 1000 .mu.m, preferably between about 750 .mu.m and about 800 .mu.m, and the thickness of the mirror body is between 50 .mu.m and 100 .mu.m. Assuming that the gap has a width of about 40 microns, the aspect ratio between the width of the gap and the distance to the support structure is about 1:20, which is particularly advantageous for the suppression of contaminants by means of a purge gas stream has exposed. In this embodiment, the individual mirrors are typically also micromirrors and the optical element is a MEMS mirror.

In a further, alternative embodiment, the width of the gap between adjacent mirror bodies is between 0.1 mm and 5 mm, preferably between 100 μm and 1 mm. In this embodiment, the individual mirrors are typically not micromirrors but conventional, macroscopically dimensioned individual mirrors.

In a further embodiment, the thickness of the mirror body is between 0.1 mm and 5 mm, preferably between 100 μm and 1 mm, and the distance between the first side of the mirror body and the support structure is between 10 mm and 500 mm, preferably between 100 mm and 400 mm. Assuming a width of the gap of about 1.0 mm and a distance of about 50 mm from the first side of the mirror body to the support structure, results in this case, an aspect ratio of 1:25, which is responsible for the suppression of contaminants has proven to be beneficial.

In another embodiment, the optical element is a facet mirror and the individual mirrors form the facet elements of the facet mirror. Facet mirrors are used, for example, in illumination systems of EUV lithography systems to produce a homogenization of the radiation generated by an EUV light source on an illumination field illuminated by the illumination system. Such facet mirrors often have a multiplicity, in particular several hundred individual mirrors, which are arranged in a typical manner in a substantially regular arrangement in a grid. Such a facet mirror may, for example, have a length extension (length × width) of more than 800 mm × 800 mm. The geometry of the facet elements is typically matched to the illumination field to be illuminated. The facet elements or the mirror bodies of the individual mirrors may, for example, have a rectangular, square, hexagonal geometry. If the faceted elements have e.g. a rectangular or square geometry, so the gaps are corresponding to the grid, i. these are arranged in mutually perpendicular rows and columns. As described above, either single micromirrors or conventionally sized mirrors may be used as individual mirrors of such a facet mirror.

A further aspect of the invention relates to an optical arrangement, in particular an EUV lithography system, comprising: at least one optical assembly as described above. The optical assembly typically has an optical element in the form of a faceted optical element or a facet mirror, the individual mirror or its mirror body mechanical or electro-mechanical components in the form of actuators can be actuated. Since these components can possibly be damaged by contaminating substances, it is favorable to protect such a facet mirror against contaminating substances.

In one embodiment, the optical assembly comprises an illumination system, wherein the optical assembly is disposed in the illumination system and wherein the optical element of the optical assembly is formed by a facet mirror of the illumination system. As has been described above, facet mirrors have mechanical or electro-mechanical components which can be protected against contaminating substances with the aid of the flushing gas flow generated by the flushing device.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawing, which show details essential to the invention, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

drawing

Embodiments are illustrated in the schematic drawing and will be explained in the following description. It shows

1 a schematic representation of an EUV lithography system with two facet mirrors,

2a -D is a schematic representation of a section of a facet mirror of 1 whose surface is exposed to contaminants, in a side view,

3 a schematic representation analogous to 2 a purge means for generating a purge gas flow passing through a gap between two adjacent facet members from the rear side thereof to the front side thereof, and

4 a perspective view of a detail of a facet mirror with a tubular purge gas line with a plurality of outlet openings for a purge gas, which are aligned with a gap between adjacent facet elements.

In the following description of the drawings, identical reference numerals are used for identical or functionally identical components.

In 1 schematically is an optical arrangement in the form of an EUV lithography system, more precisely an EUV lithography system 1 , shown. This has an EUV light source 2 for generating EUV radiation having a high energy density in an EUV wavelength range below 50 nm, in particular between about 5 nm and about 15 nm. The EUV light source 2 For example, it may be in the form of a plasma light source for generating a laser-induced plasma or as a synchrotron radiation source. Especially in the former case, as in 1 shown a collector mirror 3 used to monitor the EUV radiation of the EUV light source 2 to a lighting beam 4 to bundle and thus increase the energy density further. The lighting beam 4 has a wavelength spectrum concentrated in a narrow band wavelength range around an operating wavelength λ _B at which the EUV lithography system 1 is operated. To select the operating wavelength λ _B or to select the narrow-band wavelength range is a monochromator 12 used.

The lighting beam 4 serves to illuminate a structured object M by means of a lighting system 10 , which in the present example, four reflective optical elements 13 to 16 having. The structured object M may be, for example, a reflective mask which has reflective and non-reflective or at least less highly reflective regions for generating at least one structure on the object M. Alternatively, the structured object M may be a plurality of micromirrors which are arranged in a one-dimensional or multidimensional arrangement and which are optionally movable about at least one axis by the angle of incidence of the EUV radiation 4 to adjust to the respective mirror.

The structured object M reflects a part of the illumination beam 4 and shape a projection beam 5 which carries the information about the structure of the structured object M and that in a projection system 40 is irradiated, which generates an image of the structured object M or a respective subregion thereof on a substrate W, including in the projection system 40 four reflective optical elements 41 to 44 are arranged. The substrate W, for example a wafer, has a semiconductor material, for example silicon, and is arranged on a holder, which is also referred to as a wafer stage WS.

The first and second reflective elements in the lighting system 10 are in the present case as a facet mirror 13 . 14 formed and have a plurality of facet elements 13a -d, 14a -D in the form of individual mirrors (micromirrors), which are each arranged in a grid arrangement. In 1 are exemplary for every facet mirror 13 . 14 four faceted elements 13a - d, 14a -D shown where the illumination beam 4 or a respective sub-beam of the illumination beam 4 is reflected. The first optical element 13 is also referred to below as a field facet mirror 13 and serves to generate secondary light sources in the lighting system 10 , The second optical element 14 is typically at the location of the first optical element 13 generated secondary light sources arranged and will also be referred to as a pupil facet mirror 14 designated. On to a respective facet element 13a -D of the in 1 shown field facet mirror 13 incident partial bundle of the illumination beam 4 is at this on a respective facet element 14a -D of the pupil facet mirror 14 diverted.

As in 2 it can be seen which is a detail of the field facet mirror 13 from 1 with exemplarily five facet elements 13a -E shows has a respective facet element 13a -E of the field facet mirror 13 a plate-shaped mirror body 19a And a substantially columnar support member 18a -E on, on which the plate-shaped mirror body 19a -E is stored. A respective mirror body 19a -E has a first page 21a -E, at the one for the EUV radiation 4 reflective coating is applied, leaving the first side 21a -E a reflective surface for the EUV radiation 4 forms.

In the 2 shown plate-shaped mirror body 19a -E of the faceted elements 13a -E the field facet mirror 13 may have a rectangular geometry and an aspect ratio (x: y) of eg 1: 1, where the x-direction is perpendicular to the plane of 1 runs. The aspect ratio of the mirror body 19a -E of the faceted elements 13a -E corresponds to the aspect ratio of the illumination system 10 illuminated, for example, rectangular illumination field. It is understood that illumination fields or mirror body 19a -E of the faceted elements 13a -E with other than a rectangular geometry are also possible.

Each of the mirror bodies 19a -E of the faceted elements 13a -E of the facet mirror 13 can be tilted in the present example by an axis direction parallel to the X direction, as in 1 by way of example by two angular positions W1, W2 of the first facet element 13a of the field facet mirror 13 is indicated. In addition, the mirror body 19a -E of a respective facet element 13a If necessary, it can also be tilted by a further axis which lies in the XZ plane (drawing plane). In this way, the direction under which the illumination beam 4 on the facet elements 13a -E hits, be adjusted.

Due to the tilting, in particular, the association between the in 1 exemplified four facet elements 13a -D of the field facet mirror 13 and the four facet elements 14a -D of the pupil facet mirror 14 be changed to produce a desired illumination distribution (illumination pupil or angular distribution) at the location of the illuminated object M. Accordingly, the mirror body of the facet elements 14a - 14d of the pupil facet mirror 14 about an axis direction parallel to the X-direction and, where appropriate tiltable about another axis, which lies in the XZ plane (drawing plane).

The EUV light source 2 is formed in the example shown as a plasma light source for generating a laser-induced plasma on a target material, which is in the form of tin droplets. Part of the tin material of the EUV light source 2 In the formation of the plasma, the gas phase is formed and forms contaminants P in the form of tin contaminants, for example of tin particles or of tin compounds, in particular of tin hydrides (stananes) (Sn _x H _y ). The contaminating substances P can be found in the EUV lithography system 1 from the EUV light source 2 from to optical elements, for example to the field facet mirror 13 or to the pupil facet mirror 14 , spread and attach to these or contaminate them.

As in 2 can be seen, the field facet mirror indicates 13 a support structure 17 in the form of a plate-shaped substrate made of silicon, on which the columnar support elements 18a -E of the faceted elements 13a -E are attached or attached. At the side of the support elements 18a -E, which of the support structure 17 turned away, are the mirror body 18a -E of the faceted elements 13a -E movably mounted.

Below the support structure 17 are in the range of every facet element 13a In the example shown, two actuators each 20 in the form of electrodes for generating an electric field attached to the mirror body 19a -E of the faceted elements 13a By electrostatic attraction to tilt an axis extending in the X direction, in the region of a respective support element 18a -E runs. The facet elements 13a -E, more precisely their mirror body 19a -E can with the help of the actuators 20 independently relative to the support structure 17 shifted, more precisely tilted.

As in 2 it is obvious that the first pages are 21a -E of the faceted elements 13a -E of the field facet mirror 13 having the reflective coating, the contaminants P exposed. As in 2 is also shown, the contaminants P can not only on the first, the support structure 17 opposite side 21a -E the mirror body 19a -E deposit, but also in a gap 23 between a respective second, the support structure 17 facing side 22a -E the mirror body 19a -E and the support structure 17 is formed, because the contaminating particles P can through a respective gap 24a D, between each two adjacent mirror bodies 13a . 13b ; 13b . 13c ; 13c . 13d ; 13d . 13e is formed in the interspace 23 penetration. It is understood that in addition to a respective in 2 shown gap 24a -D, which extends in the Y direction, between adjacent in the X direction sides of the mirror body 19a -E also a respective gap extends, which extends in the X direction and through the likewise contaminating particles P in the space 23 can penetrate.

The particles P entering the space 23 can enter, on a respective support element 18a -E, on the second page 22a -E the mirror body 19a -E and / or on the supporting structure 17 of the facet mirror 13 drop. This is especially the case when individual mirror bodies 19a -E of the faceted elements 13a -E from a common, in 2 Dashed line indicated 32 be tilted out like this at the second and third in 2 shown facet element 13b . 13c the case is because in this case the gap 24b increased.

Due to the deposition of contaminants P in the form of tin particles, the electric potential at the surface of the support elements 18a -E change, causing the Aktuierung or tilting of the mirror body 19a -E of the faceted elements 13a -E through the actuators 20 is impaired. In particular, by the deposition of the contaminants P, the angular range in which the actuation of the facet elements 13a -E, more precisely from their mirror bodies 19a -E is possible to be restricted.

To prevent this, the in 3 shown example on the facet mirror 13 a rinsing device 25 provided, which for generating a purge gas stream 26 is formed by a respective gap 24a between the mirror bodies 19a . 19b , ... of two adjacent individual mirrors 13a . 13b , ... passes through. As in 3 indicated by an arrow, is the purge gas stream 26 from the second page 22a . 22b the adjacent mirror body 19a . 19b on the first page 21a . 21b the adjacent mirror body 19a . 19b directed. In 3 are for simplicity of illustration only the first and the second facet element 13a . 13b or their mirror body 19a . 19b and the gap formed between them 24a provided with reference numerals. It is understood, however, that the gas stream 26 typically through the column 24a , ... between all facets elements 13a . 13b , ... of the facet mirror 13 passes through, as in 3 indicated by corresponding arrows. It is also understood that on the support structure 17 Actuators for moving or tilting the facet elements 13a . 13b , ..., on whose representation in 3 was omitted for reasons of clarity.

To the purge gas stream 26 to produce, has the support structure 17 , which is typically formed in several parts in this case, a distribution chamber 27 on, in which a supply line 28 for supplying a purge gas 29 empties. The supply line 28 is at the distribution chamber 27 or the facet mirror 13 opposite end connected to a non-illustrated gas reservoir, from which the purge gas 29 is removed via a possibly controllable valve. In the purge gas 29 It is typically hydrogen or helium, since these gases have a low molecular mass and thus the EUV radiation 4 absorb only slightly, but in principle also other inert gases, such as nitrogen or heavier noble gases, such as argon, as a purge gas 29 be used.

The distribution chamber 27 has a plurality of outlet openings, the number of gaps between adjacent mirror bodies 19a . 19b corresponds, of which in 3 to simplify the illustration, only a first outlet opening 30a is provided with a reference numeral. The outlet openings 30a , ... are on the support structure 17 , more precisely at her the mirror bodies 19a . 19b formed, facing side. The outlet openings 30a , ... may be formed in the manner of nozzle openings already in the gap 23 a purge gas stream 26 to generate on a respective gap 24a , ... between two adjacent mirror bodies 19a . 19b , ... is aligned. The outlet openings 30a , ... may be formed in particular gap-like, with the longitudinal side of the outlet openings 30a , ... parallel to a respective gap 24a , ... between adjacent mirror bodies 19a . 19b , ... extends.

For the generation of purge gas stream 26 has a favorable effect that the width B of the respective gap 24a , ... between adjacent mirror bodies 19a . 19b , ... in the event that it is the individual mirrors 13a . 13b , ... is micromirror, comparatively low and typically between about 30 μm and 70 μm, in particular between 40 μm and 50 μm. As in 2 can be seen, the width B of the gap 24d between adjacent mirror bodies 19d . 19e measured in their basic position, in which these are not affected by the action of the actuators 20 are tilted, ie at the in 2 shown example between two mirror bodies 19d . 19e whose fronts 21d . 21e in the common plane 32 are arranged.

In the formation of the facet mirror 13 as a so-called MEMS mirror, in which as a single mirror 13a . 13b , ... Micro mirrors are used, which lies in 2 shown thickness D of the tiltable mirror body 19a , ... typically in the order of between about 50 microns and 100 microns, for example, at about 75 microns. The distance A between the first page 21a . 21b , ... the mirror body 19a . 19b , ... and the supporting structure 17 in this case is typically between about 500 microns and 1000 microns, for example, about 800 microns. The aspect ratio of gap depth to gap width is therefore about 1:20, which is for the suppression of contaminating particles P using a purge gas stream 26 has proved to be particularly favorable.

Alternatively to the formation of the first and the second facet mirror 13 . 14 ... as MEMS levels can their individual levels 13a . 13b , ... respectively. 14a . 14b , ... also be conventional (ie macroscopic) dimensioned. In this case, the width B of the gap 24a . 24b , ... between adjacent mirror bodies 19a . 19b , ... typically between about 0.1 mm and about 5 mm, for example between about 0.1 mm and 1 mm, and the thickness D of the mirror body 19a . 19b , ... is usually also in the order of between 0.1 mm and 5 mm, for example between about 0.1 mm and 1 mm. The distance between the first side of the mirror body 19a . 19b , ... and the supporting structure 17 is in this case usually between about 10 mm and about 500 mm, for example between about 100 mm and 400 mm. Also in this case results in a favorable for the suppression of contaminating particles P aspect ratio.

Other than this in 3 Shown are the facet elements 13a , ... of the facet mirror 13 typically from a peripheral edge of the support structure 17 surrounded, which the gap 23 bounded laterally, so that no contaminating particles P laterally into the gap 23 can reach. An between a border facet element, such as the first facet element 13a , and the peripheral edge of the support structure 17 formed gap can also in the manner described above with a purge gas 26 be rinsed.

The rinsing device 25 partially in the facet mirror 13 integrated, forms together with the faceted mirror 13 an optical assembly 31 , which by means of the purge gas stream 26 the penetration of contaminating particles P into the space 23 between the mirror bodies 19a . 19b , ... and the supporting structure 17 prevented. The purge gas stream 26 that from the columns 24a , ... between the faceted elements 13a . 13b , ... of the facet mirror 13 In addition, at least in part, prevents the contaminating particles P from reaching the reflecting surfaces which are the front surfaces 21a , ... the mirror body 19a . 19b , ..., so that they can not attach themselves there.

Another possibility for the realization of a flushing device 25 for generating a purge gas stream 26 in a split 24a between adjacent facet elements 13a . 13b runs is exemplary in 4 shown what a detail of a facet mirror 13 shows. In 4 The mirror bodies of four facet elements are not shown to the underlying gap 23 to show. At the in 4 example shown is in the gap 23 a tubular purge gas line 33 arranged, which has a plurality of outlet openings 30 comprising, from which the purge gas stream 26 More precisely, a respective partial flow of the purge gas stream 26 , exit. The purge gas line 33 runs parallel to the gap 24a between the adjacent mirror bodies 19a . 19b , just below the gap 24a , The outlet openings 30 are at the top of the tubular purge gas line 33 formed and thus on the gap 24a aligned.

It is understood that in 4 merely to simplify the illustration, only a single purge gas line 33 however, it is typically shown for each gap extending in the X direction 24a , ... between adjacent mirror bodies 19a . 19b , ... a separate purge gas line 33 is provided. Accordingly, a respective purge gas line is provided for each gap which extends in the Y direction between adjacent mirror bodies. The purge gas line 33 or all purge gas lines are in the example shown laterally on the support structure 17 attached and can be similar to in 3 is shown with a in the support structure 17 formed distribution chamber 27 which are the purge gas 29 the purge gas lines 33 supplies.

It is understood that in 3 and 4 only two options are shown for a purge gas flow 26 but to generate that, but a variety of other ways to generate a purge gas stream 26 exist. Basically, it is for generating the purge gas stream 26 sufficient if in the interspace 23 with the purge gas 29 there is a slight overpressure against the (vacuum) environment, in which the facet mirror 13 is arranged. The (static) pressure around the facet mirror 13 is typically between 1 Pa and 10 Pa, for example between 3 Pa and 8 Pa, in particular between 4 Pa and 6 Pa and the pressure in the gap 23 with the purge 29 is chosen so that it is greater than the ambient pressure. It is therefore not mandatory that already in the interspace 23 a purge gas stream 26 is formed on a respective gap 24a , ... is aligned. Unlike in 3 and 4 is shown, therefore, if necessary, a single outlet opening 30 be sufficient, which the purge gas 29 in the gap 23 lets enter into the columns 24a , ... between adjacent mirror bodies 19a . 19b , ... the purge gas flow 26 to create.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• US 2010/0195076 A1 [0006]
• DE 102012213927 A1 [0007]

Claims (15)

Optical assembly ( 31 ) comprising: an optical element ( 13 ) comprising: a plurality of individual mirrors ( 13a . 13b , ...), which are connected to a common support structure ( 17 ), the individual mirrors ( 13a . 13b , ...) each have a mirror body ( 19a . 19b , ...), of which the support structure ( 17 ) facing away from the first page ( 21a . 21b , ...) forms a reflective surface, and with a plurality of actuators ( 20 ) for displacement, in particular for tilting, of the mirror body ( 19a . 19b , ...) of a respective individual mirror ( 13a . 13b , ...) relative to the support structure ( 17 ), characterized by a rinsing device ( 25 ) for generating a purge gas stream ( 26 ) passing through a gap ( 24a , ...) between the mirror bodies ( 19a . 19b , ...) of at least two adjacent individual mirrors ( 13a . 13b , ...), wherein the purge gas stream ( 26 ) of one of the support structure ( 17 ) facing the second side ( 22a . 22b , ...) the mirror body ( 19a . 19b , ...) towards the first page ( 21a . 21b , ...) the mirror body ( 19a . 19b , ...) is aligned. Optical assembly according to claim 1, wherein the flushing device ( 25 ) at least one outlet opening ( 30a , ...) for the escape of purge gas ( 29 ) into a space ( 23 ) between the second page ( 22a . 22b , ...) the mirror body ( 19a . 19b , ...) and the supporting structure ( 17 ) having. Optical assembly according to claim 2, wherein at least one outlet opening ( 30a , ...) on a gap ( 24a , ...) between two adjacent mirror bodies ( 19a . 19b , ...) is aligned. Optical assembly according to one of claims 2 or 3, wherein the rinsing device ( 25 ) at least one tubular purge gas line ( 33 ), which in the space ( 23 ) parallel to a gap ( 24a , ...) between adjacent mirror bodies ( 19a . 19b , ...) runs and preferably at least one on the gap ( 24a , ...) aligned outlet opening ( 30a , ...) having. Optical assembly according to one of claims 2 to 4, wherein the rinsing device ( 25 ) at least one outlet opening ( 30a ), which on the support structure ( 17 ) is formed. Optical assembly according to one of the preceding claims, in which the rinsing device ( 25 ) is formed, a purge gas stream ( 26 ), which generates a purge gas ( 29 ) which is selected from the group comprising: hydrogen, nitrogen and noble gases. Optical assembly according to one of the preceding claims, in which the rinsing device ( 25 ) at least one supply line ( 28 ) for supplying the purge gas ( 29 ) to the optical element ( 13 ) having. Optical assembly according to one of the preceding claims, in which the mirror body ( 19a . 19b , ...) of a respective individual mirror ( 13a . 13b , ...) on one of the support structure ( 17 ) mounted pillar-shaped support element ( 18a . 18b , ...) is stored. Optical assembly according to one of the preceding claims, in which the width (B) of the gap ( 24a , ...) between adjacent mirror bodies ( 19a . 19b , ...) is between 30 μm and 70 μm, preferably between 40 μm and 50 μm. Optical assembly according to one of the preceding claims, wherein the thickness (D) of the mirror body ( 19a . 19b , ...) between 50 μm and 100 μm and the distance (A) between the first side ( 21a . 21b , ...) the mirror body ( 19a . 19b , ...) and the supporting structure ( 17 ) is between 500 μm and 1000 μm. Optical assembly according to one of claims 1 to 8, wherein the width (B) of the gap ( 24a , ...) between adjacent mirror bodies ( 19a . 19b , ...) is between 0.1 mm and 5 mm, preferably between 100 μm and 1 mm. Optical assembly according to one of Claims 1 to 8, in which the thickness (D) of the mirror bodies ( 19a . 19b , ...) between 0.1 mm and 5 mm, preferably between 100 μm and 1 mm, and the distance (A) between the first side ( 21a . 21b , ...) the mirror body ( 19a . 19b , ...) and the supporting structure ( 17 ) is between 10 mm and 500 mm, preferably between 100 mm and 400 mm. Optical assembly according to one of the preceding claims, in which the optical element has a facet mirror ( 13 . 14 ) and in which the individual mirrors ( 13a . 13b , ...; 14a . 14b , ...) the facet elements of the facet mirror ( 13 . 14 ) form. Optical arrangement, in particular EUV lithography system ( 1 ), comprising: at least one optical assembly ( 31 ) according to any one of the preceding claims. An optical assembly according to claim 14, comprising: a lighting system ( 10 ), wherein the optical assembly ( 31 ) in the lighting system ( 10 ) and wherein the optical element of the optical assembly ( 31 ) through a facet mirror ( 13 . 14 ) of the lighting system ( 10 ) is formed.

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