DE102011079837A1 - Optical system for microlithographic projection exposure system for manufacturing e.g. LCDs, has beam-splitting optic element arranged such that degree of polarization of incident light beam is lesser than specified value - Google Patents

Abstract

The system has a beam-splitting optic element for splitting a light beam incident on the beam-splitting optic element during operation of a microlithographic projection exposure system into partial beams (S101, S102), which comprise mutually orthogonal polarization directions. A diffractive optic element (DOE) generates a desired polarized illumination setting e.g. quadrupole or dipole illumination setting, for the partial beams. The beam-splitting optic element is arranged such that a degree of polarization of the incident light beam is lesser than 1, preferably lesser than 0.1. The beam-splitting optic element is designed as a polarization beam splitter (110), a sub-lambda lattice, a multi-layer membrane or a birefringent element. Independent claims are also included for the following: (1) a microlithographic exposure method (2) a method for microlithographically manufacturing micro-structured components.

Description

The invention relates to an optical system of a microlithographic projection exposure apparatus, and to a microlithographic exposure method.

Microlithography is used to fabricate microstructured devices such as integrated circuits or LCDs. The microlithography process is carried out in a so-called projection exposure apparatus which has an illumination device and a projection objective. In this case, the image of a mask (= reticle) illuminated by the illumination device is projected onto a substrate (eg a silicon wafer) coated with a photosensitive layer (photoresist) and arranged in the image plane of the projection objective to project the mask structure onto the mask transfer photosensitive coating of the substrate.

Various approaches are known for selectively adjusting specific polarization distributions in the pupil plane and / or in the reticle in the illumination device for optimizing the imaging contrast. Here, the so-called IPS value (IPS = "Intensity in Preferred State"), which describes the degree of polarization in a desired state, is of fundamental importance. In practice, an undesirable reduction of the IPS value may result, for example, from stress birefringence occurring in the optical elements or lenses of the illumination device, which may in particular lead to the polarization state becoming elliptical or indeed still the desired preferred polarization direction, but with one does not have in the desired direction polarized light component. In this case, the IPS value can be increased by compensating for this ellipticity.

Various approaches are known for obtaining a desired polarized illumination setting by rotating the polarization direction from already polarized light (for example, as a result of the use of an already polarized light-emitting laser light source) and composing the intensity distribution in the pupil plane from correspondingly polarized light components. The prior art is merely exemplary of the WO 2009/054541 A2 directed.

In practice, however, the situation may arise that at least parts of the illumination light are unpolarized. This is the case in particular in systems in which the light source generates unpolarized light from the outset, ie in a projection exposure system designed for EUV or also in an illumination system utilizing the i-line (with a wavelength of approximately 365 nm) as illuminating light.

It is an object of the present invention to provide an optical system of a microlithographic projection exposure apparatus and a microlithographic exposure method which enable the most efficient generation of a desired polarized illumination setting from at least partially unpolarized light.

This object is achieved according to the features of the independent claims.

• – eine Lichtquelle;
• – ein strahlaufspaltendes optisches Element, welches eine Aufspaltung eines im Betrieb der Projektionsbelichtungsanlage auf dieses Element auftreffenden Lichtstrahls in einen ersten Teilstrahl und einen zweiten Teilstrahl bewirkt, wobei der erste und der zweite Teilstrahl zueinander orthogonale Polarisationsrichtungen aufweisen; und
• – wenigstens einem strahlablenkenden optischen Element zur Erzeugung eines gewünschten polarisierten Beleuchtungssettings aus dem ersten Teilstrahl und dem zweiten Teilstrahl;
• – wobei das strahlaufspaltende optische Element derart angeordnet ist, dass im Betrieb der Projektionsbelichtungsanlage auf dieses strahlaufspaltende optische Element auftreffendes Licht einen Polarisationsgrad kleiner als Eins aufweist.

An optical system according to the invention of a microlithographic projection exposure apparatus has:

• A light source;
• A beam-splitting optical element which effects a splitting of a light beam impinging on this element during operation of the projection exposure apparatus into a first partial beam and a second partial beam, the first and second partial beams having mutually orthogonal polarization directions; and
• - At least one beam deflecting optical element for generating a desired polarized Beleuchtingssettings from the first partial beam and the second partial beam;
• - Wherein the beam splitting optical element is arranged such that in the operation of the projection exposure system incident on this beam splitting optical element light has a polarization degree less than one.

The invention is based on the concept of increasing the degree of polarization in a microlithographic projection exposure apparatus starting from unpolarized input light or having a low degree of polarization with as little loss of light as possible. This increase in the degree of polarization takes place via the splitting of the input light into two mutually orthogonally polarized partial beams, which are in turn "further processed" so that ultimately the desired polarized illumination setting is achieved. In this way, the degree of polarization is increased, which at the same time avoids the light losses associated with the conventionally customary use of a polarizer (which can typically be on the order of 50).

In particular, the invention does not pursue the concept, which is generally realized in conventional known approaches, of merely rotating an already existing preferred direction of polarization and thus, with the degree of polarization remaining the same (DoP = degree of polarization), only the To increase polarization purity (PP = "polarization purity"), ie within the diagram of 6 to realize a transition from right to left. Rather, the concept of the invention involves increasing the degree of polarization itself - with as little loss of light as possible (corresponding to a transition in the diagram of FIG 6 "From bottom to top"). In this case, not necessarily a transition within the same column of the diagram of 6 from bottom to top, but it can also - depending on the ultimately desired polarized illumination setting - two mutually perpendicular polarized partial beams (corresponding to those in the first line of 6 fields shown on the left or right). In other application examples, of course, the desired state of polarization also in the first line of 6 in the middle field shown polarization direction (which runs at 45 ° to the y-direction) correspond.

The relationship between the mentioned sizes polarization degree and polarization purity is given by IPS = DoP · (PP - 0.5) + 0.5 (1) where DoP denotes the degree of polarization (= "degree of polarization"), PP the polarization purity (= "polarization purity") and IPS the intensity in the desired polarization state (= intensity in preferred state ").

The invention is not limited to increasing the degree of polarization from 0% (corresponding to unpolarized light) to substantially 100% (corresponding to fully polarized light of constant polarization direction). Rather, a further advantageous application of the invention is also the degree of polarization z. B. after a present in the illumination beam mirror (which already causes a partial polarization) to increase, so for only partially polarized light. This is done according to the invention also by dividing the light beam into two partial beams with mutually orthogonal polarization states.

According to one embodiment, the beam splitting optical element is arranged such that light incident on this beam splitting optical element during operation of the projection exposure apparatus has a degree of polarization of less than 0.5, in particular less than 0.3, more particularly less than 0.1.

The desired polarized illumination setting can, for. B. have a quasi-tangential polarization distribution. Furthermore, the desired polarized illumination setting may be a quadrupole illumination setting or a dipole illumination setting.

In particular, the light source may be a light source in the form of a mercury short arc lamp that generates the i-line (with a wavelength of approximately 365 nm).

The beam deflecting element may in particular comprise a diffractive optical element (DOE).

In particular, the beam splitting element may comprise a polarization beam splitter, a sub-lambda grating, a multilayer membrane or a birefringent element.

The light source may also be an EUV plasma source. Here, the Strahlaufspaltende element as explained in more detail below z. B. have a zirconium foil.

According to one embodiment, at least one rotator for rotating the polarization state, in particular by 90 °, is arranged in the beam path of one of the two partial beams.

According to one embodiment, a diffuser is arranged in the beam path of the two partial beams.

The invention further relates to a microlithographic projection exposure apparatus having an illumination device and a projection objective, wherein the illumination device has an optical system with the features described above.

• – wobei mittels einer Lichtquelle erzeugtes Beleuchtungslicht einer Beleuchtungseinrichtung einer Projektionsbelichtungsanlage zur Beleuchtung einer Objektebene eines Projektionsobjektivs zugeführt wird, wobei die Objektebene mittels des Projektionsobjektivs in eine Bildebene des Projektionsobjektivs abgebildet wird;
• – wobei an einer Position innerhalb der Beleuchtungseinrichtung das die Beleuchtungseinrichtung durchlaufende Licht einen Polarisationsgrad kleiner als Eins aufweist; und
• – wobei der Polarisationsgrad in Lichtausbreitungsrichtung nach dieser Position erhöht wird, wobei das Licht in einen ersten Teilstrahl und einen zweiten Teilstrahl aufgespalten wird, und wobei der erste und der zweite Teilstrahl zueinander orthogonale Polarisationsrichtungen aufweisen.

According to a further aspect, the invention relates to a microlithographic exposure method,

• Wherein illuminated light generated by a light source is supplied to a lighting device of a projection exposure apparatus for illuminating an object plane of a projection lens, wherein the object plane is imaged by means of the projection lens into an image plane of the projection lens;
• - Wherein at a position within the illumination device, the light passing through the illumination device has a polarization degree less than one; and
• - Wherein the degree of polarization in the direction of light propagation is increased after this position, wherein the light is split into a first partial beam and a second partial beam, and wherein the first and the second partial beam have mutually orthogonal polarization directions.

The degree of polarization can be increased in particular by at least 0.3, more particularly by at least 0.6, in particular by 0.9, and more particularly by the value zero to the value one.

Further embodiments of the invention are described in the description and the dependent claims.

The invention will be explained in more detail with reference to embodiments shown in the accompanying drawings.

Show it:

1 a schematic representation for explaining the underlying principle of the present invention;

2 a schematic representation for explaining an embodiment of the present invention;

3 - 5 schematic representation for explaining further embodiments of the invention; and

6 a diagram for explaining an underlying objective of the invention.

1 shows a schematic representation of an arrangement for explaining the general concept of the present invention.

According to this first embodiment, unpolarized illumination light of a light source (in FIG 1 not shown) by means of a merely indicated polarization beam splitter 110 divided into two mutually orthogonally polarized light beams or partial beams S101, S102. It is the through the polarization beam splitter 110 transmitted sub-beam S102 polarized in the drawn coordinate system in the y-direction, and that on the polarization splitter 110 reflected partial beam S101 is polarized in the x direction. The unpolarized state of the onto the polarization beam splitter cube 110 incident input light is here and below symbolized by the fact that both polarization directions are drawn for this light beam.

The arrangement according to 1 further includes (without the invention being limited thereto) three deflection mirrors 120 . 130 and 140 by means of which the sub-beam S101 is again aligned parallel to the sub-beam S102. Then, as explained with reference to the further exemplary embodiments, a suitable "further processing" of at least one of the partial beams S101, S102 takes place in order to set the finally desired polarized illumination setting in the illumination device.

2 shows an embodiment in which it is in the desired, set according to the invention polarized illumination setting 203 is a quadrupole illumination setting with quasi-tangential polarization distribution, ie with a polarization distribution, in which the direction of oscillation of the electric field strength vector extends at least approximately perpendicular to the (on the drawn coordinate system in the z-direction extending) optical system axis radius. This is according to 2 in the beam path of each partial beam S101 or S102 in each case a diffractive optical element (DOE) 205 respectively. 206 arranged, which of the polarization beam splitter 110 outgoing, one of the two orthogonal polarization states having light to the appropriate for the relevant illumination setting position in the pupil plane of the illumination device directs. Effective are thus by the polarization beam splitter 110 in connection with the respective DOE 205 . 206 polarized "sub-pupils" 201 . 202 their superposition in the pupil plane the ultimately desired polarized illumination setting 203 results. Specifically, it is in the embodiment in which by the DOE 205 in conjunction with the polarization beam splitter 110 generated subpupil 201 around a horizontal dipole illumination setting with y polarization, and at the DOE 206 in conjunction with the polarization beam splitter 110 generated subpupil 202 around a vertical dipole illumination setting with x-polarization.

In other embodiments, instead of the DOE's 205 . 206 Also, one (possibly also each one) mirror assembly with a plurality of independently adjustable mirror elements are used.

The invention is also not limited to a particular realization of the polarization beam splitter 110 limited in the form of a beam splitter cube, but it can be used in principle any suitable Strahlaufspaltende element, if this is suitable for the corresponding operating wavelength.

To realize the beam splitting according to the invention in an illumination device, a so-called sub-lambda grating (ie a grating with a spacing of the grating structures below the operating wavelength) can also be used. Furthermore, a multilayer membrane may also be used in which a plurality of layers (with a width of the order of 10 nm) form a membrane, so that when they are aligned at a suitable angle (Typically below 45 °) the desired polarization-sensitive beam propagation takes place.

In other embodiments, a birefringent beam splitting element may also be employed, utilizing the property of birefringent materials in terms of spatial separation between the ordinary and extraordinary beams. A first low beam deflection by the birefringent element can be achieved by further beam deflection (s), z. B. a further deflection by about 90 ° can be increased.

The arrangement of 2 is particularly suitable for implementation in conjunction with a lighting device in which the illumination light is generated by an unpolarized light source. This may be z. B. is a mercury short arc lamp, which generates light of the i-line with a wavelength of about 365 nm. Such a mercury short-arc lamp may typically, such as DE 44 12 053 A1 or EP 0 658 810 A1 be arranged at a focal point of an elliptical mirror, which collects the emitted light in the second focal point.

However, in other exemplary embodiments, the invention can also be implemented in conjunction with a lighting device designed for a working wavelength in the EUV range (ie, at wavelengths of less than 15 nm), as shown only schematically in FIG 3d is shown.

According to 3d points in a projection exposure system designed for EUV 375 a lighting device 380 a first facet mirror 381 with a plurality of first reflective facet elements 382 and a second facet mirror 383 with a plurality of second reflective facet elements 384 on. At the first facet mirror 381 becomes the light of a light source unit 385 , which is a plasma light source 386 and a collector mirror 387 includes, steered. In the light path after the second facet mirror 383 are a first telescope mirror 388 and a second telescope mirror 389 arranged. In the light path below is a deflection mirror 390 arranged, the radiation impinging on him on an object field 391 in the object plane OP of a six-mirror M1-M6 projection lens 395 directs. At the place of the object field 391 is a reflective structure-bearing mask M arranged using the projection lens 395 is mapped into an image plane IP.

To explain an implementation of the invention in such a designed for EUV lighting device shows the schematic representation according to 3a again, the inventive decomposition of an initially unpolarized light beam S300 (as generated by an EUV plasma light source) in two light beams S301 and S302 with mutually orthogonal polarization states, in the illustrated embodiment, the light beam S302 in the y direction and the light beam S301 in x direction is polarized in the illustrated coordinate system. The beam splitting element, the decomposition into the mutually orthogonal polarization states causing element 310 can be realized by a zirconium foil, wherein the thickness of the zirconium foil can be only about 50 microns by way of example. This zirconium foil is arranged in the beam path at an angle of 45 ° to the direction of light propagation (= z-direction in the drawn coordinate system). This angle corresponds to the Brewster angle, since the refractive index of zirconium in EUV is close to 1.

The use of zirconium foils in EUV lithography is e.g. B. off EP 1 356 476 B1 and DE 10 2008 041 801 A1 for the realization of spectral filters for filtering out unwanted portions of the electromagnetic radiation, wherein, as in EP 1 356 476 B1 described zirconium foil may also be arranged between two silicon layers to prevent oxidation of the zirconium material.

By the zirconium foil used in the embodiment of the present invention, the s-polarized light is largely reflected, and the p-polarized light is largely transmitted. Specifically, by means of such, arranged at the Brewster angle zirconia - taking into account the attenuation due to absorption in the material - a transmission of about (70-80)% for the p-polarized light component and a reflection of about also (70-80) % for the s-polarized light component.

In order to again according to the invention to minimize a loss of light when increasing the degree of polarization, the sub-beams generated perpendicularly to one another as described above can each be supplied to one of two sub-modules provided parallel to one another within one and the same illumination device. These submodules can z. B. each having a separate field facet mirror, so that in the arrangement of 3a Exiting partial beams with mutually orthogonal polarization to meet different field facet mirror. The field facet mirrors produce different intensity distributions (thus effectively taking over the function of the DOEs 205 . 206 the arrangement of 2 true) before re-coupling into a single lighting device.

Alternatively, the according to 3a for illumination light with a working wavelength in the EUV, polarized perpendicular to each other Sub-beams are also coupled from the outset in two separate EUV lighting devices.

3b shows an embodiment in which the generated by splitting the first unpolarized light, orthogonal to each other polarized partial beams S301 and S302 via a first and second facet mirror 330 . 340 on facets of a third facet mirror 350 be steered. The facets of the third facet mirror 350 can switch between at least two switching positions, in which they light each of a facet of the first facet mirror 330 or the second facet mirror 340 catch. As a result, in this way, by suitable choice of the switching positions of the facet facets of the third facet mirror 350 starting from the partial beams S301 and S302 different polarized lighting settings can be realized.

3c shows a further embodiment in which the generated by splitting the first unpolarized light, orthogonal to each other polarized partial beams S301 and S302 via a first facet mirror 360 with two spatially separated areas (in 3c symbolized by the dashed line in the facet mirror 360 ) on facets of a second facet mirror 370 be steered. Its facets can change between at least two switching positions, in which they light each of a facet of the areas of the first facet mirror 360 catch. As a result, in this way, by suitable choice of the switching positions of the facets of the second facet mirror 370 starting from the partial beams S301 and S302 different polarized lighting settings can be realized.

4a shows a further embodiment of the invention, wherein 2 analogous or substantially functionally identical elements are designated by "300" increased reference numerals. The arrangement of 4a is analogous to that of 2 also particularly suitable for implementation in conjunction with a lighting device in which the illumination light is generated by an unpolarized light source using the i-line and with a working wavelength in the DUV range.

The structure according to 4a differs from the one according to 2 in that ultimately a polarized illumination setting 401 is produced in the form of a dipole illumination setting with a polarization preferred direction (extending in the drawn coordinate system in the y direction), ie a so-called horizontal dipole illumination setting with y polarization.

For this purpose, the arrangement according to 4a instead of the DOE's 205 . 206 out 2 in the beam path of the sub-beam S401 a 90 ° rotator 450 and a diffuser arranged in the beam path of both partial beams S401, S402 460 on. The diffuser 460 can be realized for example as a diffuser or as a honeycomb condenser. The 90 ° rotator 450 can, for example, optically active material (in particular crystalline quartz with the direction of light propagation or z-direction parallel orientation of the optical crystal axis) or by utilizing linear birefringence (ie as lambda / 2 plate of linear birefringent, optically uniaxial material or in a known manner two lambda / 2 plates with at least 45 ° relative to each other twisted optical crystal axis composed) be realized. Furthermore, the arrangement according to 4a instead of under construction 2 provided DOE's 205 and 206 only a single DOE 470 on, which in the beam path of both partial beams S401 and S402 and in the light propagation direction downstream of the diffuser 460 is arranged and the respective (as in 4 schematically shown now in the same way, namely in the y direction) linearly polarized partial beams S401 and S402 to the desired areas in the pupil plane of the illumination device for the realization of in 4a schematically illustrated illumination settings 401 directs.

Of course, alternatively - analogous to 2 - In each case a separate DOE be provided for both partial beams S401 and S402. Furthermore, as an alternative to the in 4a also shown arrangement on the diffuser 460 dispensed with and a mixture of the two partial beams S401 and S402 alone be achieved by means of a suitable DOE's.

In further embodiments, in a modification of the in 4a For the realization of the 90 ° rotation of the polarization direction for the sub-beam S401, a three-dimensional mirror arrangement with three (skew) mirrors is also shown 481 . 482 . 483 be used as they are in 4b shown schematically and z. B. off WO 2009/152867 is known. Through the mirror 481 - 483 becomes analogous to 4a a rotator is formed, which is also usable in conjunction with a designed for EUV lighting device.

5 serves in a schematic representation for explaining a further embodiment in which the inventive 90 ° rotation of the polarization direction can be realized for one of two partial beams. This embodiment is analogous to the above with reference to 2 and 4 described embodiments also particularly suitable for implementation in conjunction with a lighting device, at which the illumination light is generated by an unpolarized light source utilizing the i-line and having a working wavelength in the DUV range.

In the arrangement of 5 becomes the at the beam splitting element 510 reflected partial beam S501 (which is polarized relative to the drawn coordinate system in the x direction) twice through a lambda / 4-plate 520 whose fast axis is oriented at 45 ° to the polarization direction of the incident light. Since the double-passing lambda / 4 plate effectively acts as a lambda / 2 plate, a 90 ° rotation of the polarization state for the sub-beam S501 is realized. This is done via a light propagation direction based on the sub-beam S501 after the lambda / 4-plate 520 arranged mirrors 530 , which relative to the z-direction or to the original light propagation direction of the light beam S500 by a preferably small angle of z. B. is tilted α <10 °. After passing through the lambda / 4 plate twice 520 and thus completed rotation of the polarization direction by about 90 ° causes another mirror 540 a renewed deflection parallel to that after passing through the beam splitting element 510 already partial beam S502 polarized in the y-direction, so that as a result substantially the entire, in the arrangement of 5 coupled illumination light with uniform polarization state, namely with a constant direction of polarization in the y direction, is available.

Of course, in the arrangement of 5 also instead of the twice passed Lambda / 4 plate 520 a simply traversed lambda / 2 plate can be provided in order to achieve a rotation of the polarization direction by about 90 ° for the sub-beam S501.

While the invention has been described with reference to specific embodiments, numerous variations and alternative embodiments will become apparent to those skilled in the art. B. by combination and / or exchange of features of individual embodiments. Accordingly, it will be understood by those skilled in the art that such variations and alternative embodiments are intended to be embraced by the present invention, and the scope of the invention is limited only in terms of the appended claims and their equivalents.

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

• WO 2009/054541 A2 [0004]
• DE 4412053 A1 [0039]
• EP 0658810 A1 [0039]
• EP 1356476 B1 [0043, 0043]
• DE 102008041801 A1 [0043]
• WO 2009/152867 [0053]

Claims (16)

Optical system of a microlithographic projection exposure apparatus, having • a light source; A beam splitting optical element ( 110 . 310 . 410 . 510 ), which causes a splitting of a light beam impinging on this element during operation of the projection exposure apparatus into a first partial beam (S101, S301, S401, S501) and a second partial beam (S102, S302, S402, S502), the first and the second partial beam have mutually orthogonal polarization directions; and at least one beam-deflecting optical element ( 205 . 206 . 330 . 340 . 350 . 360 . 370 . 470 . 530 . 540 ) for generating a desired polarized illumination setting from the first partial beam (S101, S301, S401, S501) and the second partial beam (S102, S302, S402, S502); Wherein the beam splitting optical element ( 110 . 310 . 410 . 510 ) is arranged such that in the operation of the projection exposure system incident on this beam splitting optical element light has a polarization degree less than one. Optical system according to claim 1, characterized in that the beam splitting optical element ( 110 . 310 . 410 . 510 ) is arranged such that in the operation of the projection exposure system incident on this beam splitting optical element light has a degree of polarization less than 0.5, in particular less than 0.3, more particularly less than 0.1. Optical system according to claim 1 or 2, characterized in that the desired polarized illumination setting has a quasi-tangential polarization distribution. An optical system according to any one of claims 1 to 3, characterized in that the desired polarized illumination setting is a quadrupole illumination setting or a dipole illumination setting. Optical system according to one of claims 1 to 4, characterized in that the light source generates unpolarized light. Optical system according to one of the preceding claims, characterized in that the light source is a mercury short arc lamp. Optical system according to one of the preceding claims, characterized in that the beam-deflecting element ( 205 . 206 . 470 ) has a diffractive optical element (DOE). Optical system according to one of the preceding claims, characterized in that the beam splitting element comprises a polarization beam splitter, a sub-lambda grating, a multilayer membrane or a birefringent element. Optical system according to one of claims 1 to 5, characterized in that the light source is an EUV plasma source. Optical system according to claim 9, characterized in that the beam splitting element ( 310 ) has a zirconium foil. Optical system according to one of the preceding claims, characterized in that in the beam path of one of the two partial beams at least one rotator ( 450 . 480 ) is arranged for rotation of the polarization state, in particular by 90 °. Optical system according to one of the preceding claims, characterized in that in the beam path of the two partial beams a diffuser ( 460 ) is arranged. Microlithographic projection exposure apparatus with an illumination device and a projection objective, characterized in that the illumination device has an optical system according to one of the preceding claims. Microlithographic exposure method, Wherein illuminating light generated by means of a light source is supplied to a lighting device of a projection exposure apparatus for illuminating an object plane of a projection objective, the object plane being imaged by the projection objective into an image plane of the projection objective; Wherein, at a position within the illumination device, the light passing through the illumination device has a polarization degree less than one; and Wherein the degree of polarization in the light propagation direction is increased after this position, the light being split into a first sub-beam (S101, S301, S401, S501) and a second sub-beam (S102, S302, S402, S502), and wherein the first and the second sub-beams second sub-beam mutually orthogonal polarization directions. Microlithographic exposure method according to claim 14, characterized in that the degree of polarization is increased by at least 0.3, in particular by at least 0.6, more particularly by 0.9, and further in particular by the value zero to the value one. A method for the microlithographic production of microstructured components comprising the following steps: providing a substrate on which at least partially a layer of a photosensitive material is applied; Providing a mask having structures to be imaged; Providing a microlithographic projection exposure apparatus according to claim 13; and projecting at least a portion of the mask onto a portion of the layer using the projection exposure apparatus.

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