DE102011077185A1 - Optical assembly of projection exposure system for manufacturing semiconductor device, has filter comprising grid strips that are provided in filter to absorb or to reflect the stray light outside the beam paths - Google Patents

Abstract

The optical assembly has a light beam source (2) from which several optical beam paths (3) are extended towards a micro mirror array (6) along preset direction. A filter (4) is arranged with respect to the beam paths so as to absorb or to reflect the scattered light beams. The grid strips (8) are provided in filter to absorb or to reflect the stray light outside the beam paths. Several mirrors (5) are provided infront of the micro mirror array. An independent claim is included for projection exposure system.

Description

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to an optical arrangement comprising a light beam source, a plurality of beam paths extending from the light beam source, along the beam paths light beams extend when the light beam source is in operation, and at least one filter, which is arranged with respect to the beam paths, at least one or more light beams are absorbed and / or reflected. Moreover, the present invention relates to corresponding filters and a projection exposure apparatus for microlithography with a corresponding optical arrangement and such a filter.

STATE OF THE ART

In projection exposure systems for microlithography, by means of which the smallest structures for microelectronics, microsystems technology or nanotechnology can be produced, illumination systems are used which may have so-called multi-mirror arrays (MMA). The multi-mirror arrays, which are also known as MOEMS (micro-optical electro-mechanical systems) due to their structure and function, comprise thousands of small mirrors which, by reflecting the working light of the projection exposure apparatus, set a specific illumination setting by setting a specific light distribution in a pupil plane enable. The mirrors of the multi-mirror arrangements can be set individually in their tilt, so-called monitoring systems monitor whether the appropriate settings are made properly.

In this case, working light of the projection exposure apparatus is understood as meaning any suitable electromagnetic radiation for producing the microstructures or nanostructures.

For various reasons, such as problems in the lithographic manufacturing process of the multi-mirror assembly, problems with the control electronics, problems with the monitoring system, contamination during operation and so on, individual mirrors of the multi-mirror assembly may already fail at the time of manufacture or subsequently during operation , The failed mirrors, which are also referred to as so-called dead mirrors, can then no longer be brought to a desired position and the working light incident on these mirrors is reflected in an undesired or uncontrolled manner. This can lead to intolerable deviations from the illumination settings in the pupil plane, which altogether negatively influence the imaging properties.

Accordingly, an attempt has already been made to solve this problem.

According to the prior art, the problem with defective mirrors is solved by avoiding that light can fall on the defective mirror, so that no uncontrolled reflection of the light can take place. For this purpose, the incident light is separated by a micro-optical focusing in a plurality of light beams, which are directed with nearly parallel beam direction side by side and one behind the other on the mirrors of the multi-mirror arrangement that each light beam strikes a mirror. Now, if a mirror is defective, the associated light beam can be hidden by a filter for the defective mirror. Accordingly, the mirror is also referred to as dead mirror blocking filter (DMBF).

According to the prior art, the corresponding filters are designed so that a chromium coating is applied to a glass plate in the areas in which the light beam that is to be hidden, so that the light beam to be blended by absorption and / or reflection at an impact was hindered on the broken mirror. The filter is placed between the focusing array and the Mehrfachspiegelandordnung so that the opaque coating in the corresponding areas of the light beams, which are directed to defective mirror fades out.

Alternatively, it has been proposed in the prior art to realize a corresponding filter with a grid arrangement, wherein the light beams should pass through the openings of the grid unhindered, while in the areas in which the light is to be hidden, the grid opening are closed by opaque material should.

In such a lattice structure, however, according to the prior art, the lattice bars is attempted to be as small as possible in order to avoid interaction with the light beams which are to pass through the lattice fields.

However, in an optical arrangement having a multi-mirror arrangement in which a plurality of light beams are to meet individual mirrors, there is still a desire To achieve an improvement in imaging quality, since it has been shown that despite the blockade filter described above, an undesirably high proportion of unwanted light (false light) is located after reflection on the multiple mirror arrangement in the beam path.

DISCLOSURE OF THE INVENTION

OBJECT OF THE INVENTION

It is therefore an object of the present invention to provide an optical arrangement with a plurality of light beams and a corresponding filter for hiding individual light beams, which avoids the problems with stray light and as possible provides only the desired light available, for example, to a downstream multi-mirror arrangement. At the same time, however, the optical arrangement and the corresponding filter should be simple and easy to handle.

TECHNICAL SOLUTION

This object is achieved by an optical arrangement having the features of claim 1 and a projection exposure apparatus having the features of claim 11 and filters having the features of claims 12 or 13. Advantageous embodiments are the subject of the dependent claims.

The invention is characterized in that an optical arrangement is provided in which the filter used has an additional function compared with the known filter, namely the function of absorbing and / or reflecting scattered light in order to block out scattered light which is emitted, for example, at the light beam source, such as B. a Fokussierarray arises. The invention makes use of the fact that not only light that should actually be hidden, can contribute to unwanted stray light, but also scattered light that arises at a Fokussierarray.

Accordingly, such a filter according to the invention comprises means for absorbing and / or reflecting stray light outside the beam paths provided for the light beams in the optical arrangement.

In this case, the beam paths can be defined such that the beam paths correspond to the theoretical geometric propagation of the light, which is provided according to the optical design of the optical arrangement. According to such a definition, all light outside the beam paths would be stray light. In addition, the beam paths can be defined so that a certain light intensity must be exceeded during operation of the optical arrangement within the beam path, so that light below a certain light intensity would be defined as light outside the beam paths and thus again as stray light. A combination of both definitions of the beam paths for the light beams is possible.

The means for absorbing and / or reflecting scattered light can be formed by appropriate absorption and / or reflection surfaces for scattered light (scattered light absorption and / or reflection surfaces). The scattered light absorption and / or reflection surfaces can be arranged transversely to the absorption and / or reflection surfaces for the radiation beam (beam absorption and / or reflection surfaces), ie along the beam direction of the beam paths and / or parallel or in alignment with the light beam absorption - and / or reflection surfaces.

The means for absorbing and / or reflecting stray light, d. H. the scattered light absorption and / or reflection surfaces can be formed by opaque connecting wall regions between two or more light beam absorption and / or reflection surfaces.

The means for absorbing and / or reflecting scattered light or the scattered light absorption and / or reflection surfaces can fill the space between the beam paths in an opaque manner at least partially transversely to the beam direction of the beam bundles or beam paths in order to block out any scattered light outside the beam paths. In particular, the corresponding absorption and / or reflection surfaces can be adapted individually to the corresponding optical arrangement, that is to say their position and orientation are aligned with the requirements of the optical arrangement. In such an individual arrangement of the absorption and / or reflection surfaces for both the scattered light and the light beam, the corresponding surfaces can thus be arranged without a regular structure.

Alternatively, however, it is also possible to provide a grating structure which has a regular arrangement of grating fields, wherein one grating field can be assigned to one beam path so that a light beam can pass through the grating field or, if the grating field is closed, the radiation beam is correspondingly blanked out can be. The grating fields are limited by corresponding grating webs, the web width is now not chosen more minimal but contrary to known grating filters of the prior art, but with a web width, the one ensures maximum absorption and / or reflection of stray light as possible. Since the lattice webs themselves can neither be sources of scattered light by corresponding diffraction of light, the lattice webs can be designed so that apodization is utilized, ie they have a high degree of transmission of light at their edges and the transmittance to the central regions of the lattice web decreases. As a result, it is possible to use particularly wide grid webs, since the interaction with the light beam bundles at the edges is low due to the high degree of transmittance, while in the middle regions the grid webs can bring about good absorption and / or reflection of scattered light.

Accordingly, in general, the absorption and / or reflection surfaces for scattered light can have a change in the transmittance in order to allow more light to pass through, especially in the edge regions, while strong fading takes place in central regions. In particular, a Gaussian distribution of the transmittance over the scattered light absorption and / or reflection surface can be provided here.

In the case of scattered light with a large scattering angle, in particular scattered light absorption and / or reflection surfaces can be used which extend parallel to the beam direction of the beam paths. In addition, it is also possible to arrange several filters along the beam direction of the beam paths one behind the other.

An embodiment of a filter with an absorption and / or reflection surface along the beam direction of the beam paths can be realized by a so-called tube filter, in which a plurality of tubes are arranged side by side with the axial longitudinal axes parallel to each other. Through the tubes, the light beams can pass through, while scattered light, in particular with a large angle of scatter can not pass the tubes due to the oblique angle of incidence.

In order to avoid reflection of the scattered light in the tubes, the inner surface of the tubes may be formed in particular with a light-absorbing material.

The tubes can be adapted to the beam paths correspondingly be formed so that they taper.

The absorption and / or reflection surfaces for scattered light and / or for light ray bundles can be formed by a self-supporting structure or arranged on a transparent support, for example on a glass pane.

A corresponding optical arrangement can be used in particular in a projection exposure apparatus for microlithography, it being understood that the term light in the present application, any electromagnetic radiation is understood and the translucent or opaque materials are tuned to the wavelength range of light accordingly.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings show in a purely schematic manner in FIG

1 a representation of a light beam assembly, which is generated by a focusing (light beam source) and directed to a multi-mirror assembly;

2 a plan view of a filter in the direction of the incident light beams, as in 1 is used;

3 a side view of a light beam arrangement with a Fokussierarray (light beam source) and a Mehrfachmikrospiegelanordnung, which illustrates the generation of scattered light.

4 a side view of a light beam arrangement according to the representation of 1 and 2 ;

5 a representation of filter arrangements in the sub-images (A) and (B) in the direction of the incident light beams;

6 an illustration of a light beam arrangement in side view to illustrate the problem with stray light, which has large scattering angles;

7 a side view of a light beam assembly having a plurality of filter elements to overcome the problem of scattered light with a large scattering angle; and in

8th a representation of a light beam arrangement in side view with a further embodiment of a filter according to the invention.

EMBODIMENTS

Further advantages, characteristics and features of the invention will become apparent in the following description of the embodiments with reference to the accompanying figures.

The 1 shows a multiple mirror arrangement 6 in which a variety of mirrors 5 one behind the other and next to each other in a field (array) are arranged, with each of the mirrors 5 a ray of light 3 is directed by the mirror 5 is mirrored in a pupil plane of the illumination system of a projection exposure apparatus for semiconductor lithography. This makes it possible to make the illumination settings variable, since light beams can be completely reflected out of the beam path or a different number of light beams can be focused in certain areas of a pupil plane.

However, there is a multiple mirror arrangement 6 as they are in 1 is shown only schematically, the problem is that at a plurality of mirrors 5 there is a likelihood that mirrors will fail during production or during subsequent operation, so that they can no longer be controlled. This leads to the fact that uncontrolled light rays are contained in the beam path. However, this should be avoided in terms of imaging properties. Accordingly, in the arrangement which is in 1 shown is a filter 4 provided with the specific light rays 3 can be hidden from the beam path, so no light on correspondingly defective mirror 5 meets. The suppression of the light rays in the filter 4 can be generated by appropriate fields which are opaque to the light and absorb and / or reflect the corresponding light.

The light beams 3 be through a focusing array 2 generated, which is indicated purely schematically with a plurality of optical lenses. Through the Fokusierarray 2 becomes the incident light 1 divided into a plurality of discrete light beams which extend along the beam paths predetermined by the focusing array. The beam paths of the optical arrangement with the focusing array 2 are arranged with the beam directions almost parallel to each other behind each other and side by side in a direction transverse to the beam direction.

The filter 4 the optical arrangement is in 2 shown in a plan view and in the beam direction of the incident light beam 3 , In the plan view of 2 it can be seen that the filter 4 a grid arrangement 10 includes, which in the image vertically and horizontally extending webs 8th is formed. The bridges 8th are spaced apart from each other so that between the webs fields 7 are defined, which are the light beams 3 are assigned so that the light beams 3 each individually in the area of individual fields 7 on the filter 4 to meet.

The fields 7 can now be more different in translucent fields 12 and opaque fields 11 , the light rays striking them 3 Hide from the beam path and prevent the light beams 3 on the mirror 5 the multi-mirror arrangement 6 to meet.

The grid bars 8th are in areas between the light beams 3 arranged and define with your distance d the lattice constant of the grid array 10 or the dimension of the fields 7 , The width B of the grid bars 8th is chosen so that the light beams are not on the grid bars 8th to meet.

There, as in 3 however, the focusing array is not just light beams 3 generated, which are used as useful light, but also undesirable stray light 13 is generated, the width B of the grid bars 8th chosen so that as much stray light 13 is filtered out. In 4 this is exemplified in a side view, wherein in addition to a light beam 3 pointing to a broken mirror 5 the multiple mirror array would be directed through the grid bars 8th also stray light 13 is blocked, so it is not on the mirror 5 the multi-mirror assembly may fall.

In the 5 is shown by way of example in the partial images (A) and (B), as in a further embodiment of the mirror according to the invention in addition to those of the focusing array 2 generated light beams and stray light can be hidden.

In the partial image (A) are several fields 11 represented, for example, are produced by a corresponding chromium coating on a glass substrate and hide in the corresponding areas light beams.

In order to hide additional stray light, in the embodiment of a filter according to the invention, as shown in the partial image (B), in addition to the absorption and / or reflection surfaces 11 for the light beam (light rays absorption and / or reflection surfaces 11 ) additional absorption and / or reflection surfaces 14 for the scattered light (scattered light absorption and / or reflection surfaces 14 ) between the light beam absorption and / or reflection surfaces 11 intended. The scattered light absorption and / or reflection surfaces 14 act in the same way as the grid bars 8th in the embodiment of the 2 and 4 However, in the case of the filter 5 (B) no lattice structure or grid structure must be provided, but the light rays absorption and / or reflection surfaces 11 and the stray light absorption and / or reflection surfaces 14 can be arranged arbitrarily. In this way, the advantage of the present invention, namely the hiding unwanted stray light, at least partially be satisfied even if the provision of a grid structure due to the dimensions of the light beam bundles and their mutual distances and correspondingly thin grid struts and difficulties in adjusting a corresponding filter can not be used.

Around the grid web width B of the grid webs 8th of the filter 4 out 2 To make as big as possible to hide much stray light, the grid bars 8th be made of a material which has different degrees of transmission for the light. So can the grid bars on the edge 8th have a high transmittance, while in the middle of the transmittance can be lower. As a result, the requirements for the adjustment of the filter, so the exact placement of the filter can be reduced. In addition, the generation of stray light at the grating structure of the filter can be reduced.

The 6 shows in a side view of a light beam arrangement another problem of a corresponding optical arrangement. In stray light 13b With a large scattering angle, the scattered light absorption and / or reflection surfaces of a filter may be sufficient 4 , For example in the form of grid bars 8th no longer look for an impingement of large-angle scattered light 13b on the mirrors of the multiple mirror array 5 to prevent. Only small angle stray light 13a is hidden by the filter.

To solve this problem you can use several filters 4a . 4b . 4c be arranged in the beam direction one behind the other, so that also large-angle scattered light 13b can be hidden.

In addition to several filters or filter elements 4a . 4b . 4c can also have a single filter 40 be provided in the form of a tube filter, in which a plurality of tubes can be arranged with their axial directions parallel to each other next to each other and one behind the other transverse to the beam direction of the beam. The tubes 41 . 42 . 43 . 44 of the filter 40 can according to the beam path of the light beams 3 be tapered and be formed on the tube inner sides with light-absorbing material to a reflection of the scattered light 13 in the tubes 41 . 42 . 43 . 44 to avoid. By a sufficiently large dimensioning of the tubes 41 . 42 . 43 . 44 in the axial direction, it is also for large-angle scattered light 13b no longer possible through the openings of the filter 40 get through and on the mirrors of the multiple mirror arrangement 5 hold true.

Although the present invention has been described in detail with reference to the accompanying embodiments, it will be understood by those skilled in the art that the invention is not limited to these embodiments, but rather modifications are possible in the manner that individual features omitted or made a different combination of features without departing from the scope of the appended claims. In particular, the present invention includes all combinations of all presented features.

Claims (13)

Optical arrangement with a light beam source ( 2 ), a plurality of beam paths that extend from the light beam source, wherein along the beam paths light beams ( 3 ) run when the light beam source is in operation, and at least one filter ( 4 . 40 ) arranged with respect to the beam paths so that at least one or more light beams are absorbed and / or reflected, characterized in that the filter comprises means ( 8th . 14 ) for absorbing and / or reflecting scattered light outside the beam paths and / or several filters ( 4a . 4b . 4c ) are arranged one behind the other along the beam paths for absorption and / or reflection of scattered light. Optical arrangement according to claim 1, characterized in that the filter has at least one absorption and / or reflection surface ( 11 ) for absorbing and / or reflecting at least one light beam ( 3 ), which is arranged transversely to the beam direction of the beam path (s), and that the means for absorption and / reflection ( 8th . 14 ) of stray light through opaque wall areas ( 8th . 14 ) of the filter, which are arranged transversely to the absorption and / or reflection surface along the beam direction of the beam paths and / or parallel or in alignment with the absorption and / or reflection surface transversely to the beam paths. Optical arrangement according to Claim 1 or 2, characterized in that the means for absorbing and / or reflecting scattered light comprise at least one light-impermeable connecting wall region ( 14 ) between two absorption and / or reflection surfaces. Optical arrangement according to one of Claims 1 to 3, characterized in that the means ( 8th . 14 ) for the absorption and / or reflection of scattered light at least partially transversely to the beam direction of the beam paths fill the space between the beam paths opaque, in particular individually adapted to the position of the beam paths. Optical arrangement according to one of Claims 1 to 4, characterized in that the means ( 8th ) are formed for absorption and / or reflection of scattered light by a lattice structure which comprises a multiplicity of lattice fields ( 7 ), one of which is associated with a beam path and by grid bars ( 8th ) is limited, the web width is chosen so that they are suitable for the absorption and / or reflection of stray light. Optical arrangement according to one of Claims 1 to 4, characterized in that the means ( 8th . 14 ) for the absorption and / or reflection of scattered light on their absorption and / or reflection surface for scattered light have a change in the transmittance. Optical arrangement according to one of claims 1 to 6, characterized in that the absorption and / or reflection surface ( 8th . 14 ) for scattered light at the edge has a higher transmittance than in the middle of the absorption and / or reflection surface for scattered light, and in particular a Gaussian distribution of the transmittance over the absorption and / or reflection surface for scattered light, preferably above the web width of a grid web of a lattice structure given is. Optical arrangement according to one of claims 1 to 7, characterized in that the filter ( 40 ) one or more tubes ( 41 . 42 . 43 . 44 ) made of opaque material, which are arranged so that in each case a light beam passes along a beam path through the tube or is blocked by a tube disposed in the absorption and / or reflection surface, in particular the axial extent of the tubes is greater than the diameter the pipe opening is. Optical arrangement according to claim 8, characterized in that the tubes ( 41 . 42 . 43 . 44 ) are tapered and / or have a light-absorbing surface on the inside of the tube. Optical arrangement according to one of the preceding claims, characterized in that the absorption and / or reflection surfaces ( 8th . 14 ) for scattered light and / or the absorption and / or reflection surfaces ( 11 ) form a self-supporting structure for the light beams or are applied to a transparent support. Microlithographic projection exposure apparatus with an optical arrangement according to one of the preceding claims. Filter for an optical arrangement, in particular for an optical arrangement according to one of claims 1 to 10, characterized in that the filter ( 4 ) has a grid structure with a plurality of intersecting lands that include fields that are transmissive or impermeable to light of a particular wavelength or wavelength range, the lands having a change in transmittance over the land width. Filter for an optical arrangement, in particular for an optical arrangement according to one of claims 1 to 10, characterized in that the filter ( 40 ) comprises one or more tubes of opaque material arranged with their longitudinal axes parallel or nearly parallel to each other, wherein the axial extent of the tubes is greater than the diameter of the tube opening and the tube inner side has a light-absorbing surface.

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