Optical system, in particular of a microlithographic projection exposure apparatus

1. An optical system comprising an optical system axis and a polarization-influencing optical arrangement, wherein said polarization-influencing optical arrangement comprises:

at least one polarization-influencing optical element which comprises an optically active material having an optical crystal axis and is of a thickness profile which varies in the direction of said optical crystal axis; and

a position manipulator for manipulation of the position of said polarization-influencing optical element, wherein the polarization manipulator is adapted to cause rotation of the polarization-influencing optical element about an axis of rotation, wherein said axis of rotation is arranged at an angle of 90°±5° relative to the optical system axis.

2. The optical system of claim 1 wherein the polarization-influencing optical element is adapted in at least one position of the polarization-influencing optical element to convert a linear polarization distribution with a preferred polarization direction that is constant over the light beam cross-section of a light beam passing through the polarization-influencing optical element into an at least approximately tangential polarization distribution.

3. The optical system of claim 1 wherein the optically active material is crystalline quartz.

4. The optical system of claim 1 wherein the polarization-influencing optical element has an element axis and the thickness profile is dependent only on the azimuth angle, wherein the azimuth angle is related to a reference axis which is perpendicular to the element axis and intersects the element axis.

5. The optical system of claim 4 wherein the polarization-influencing optical element is composed of at least two subelements which each have a thickness profile dependent only on the azimuth angle.

6. The optical system of claim 4 wherein an azimuthal section through the thickness profile for an azimuth angle 10°<θ<170° and for an azimuth angle 190°<θ<350° and for a constant spacing r from the element axis, is a linear function of the azimuth angle θ, wherein said linear function has at least approximately a gradient



m



=

180

⁢

°

απ

⁢

⁢

r

,

wherein α is the specific rotational capability of the optically active crystal.

7. The optical system of claim 6 wherein the azimuthal section for the azimuth angles θ=0° and θ=180° each have an approximately abrupt rise by

180

⁢

°

α

.

8. The optical system of claim 4 wherein the polarization-influencing optical element is composed of four subelements which each have a thickness profile dependent only on the azimuth angle.

9. The optical system of claim 4 wherein an azimuthal section through the thickness profile for an azimuth angle 10°<θ<80°, for an azimuth angle 100°<θ<260° and for an azimuth angle 280°<θ<350° and for a constant spacing r from the element axis, is a linear function of the azimuth angle θ, wherein said linear function has at least approximately a gradient

m

=

-

180

⁢

°

απ

⁢

⁢

r

,

wherein α is the specific rotational capability of the optically active crystal.

10. The optical system of claim 9 wherein the azimuthal section for the azimuth angles θ=90° and θ=270° each have an approximately abrupt rise by

180

⁢

°

α

.

11. The optical system of claim 1 further comprising a 90° rotator.

12. A microlithographic projection exposure apparatus comprising an illumination system and a projection objective, wherein the illumination system and/or the projection objective comprise an optical system as set forth in claim 1 .

13. A process for the microlithographic production of microstructured components comprising the following steps:

providing a substrate to which a layer of a light-sensitive material is at least partially applied;

providing a mask having structures which are to be imaged;

providing a microlithographic projection exposure apparatus as set forth in claim 12 ; and

projecting at least a part of the mask on to a region of the layer using the projection exposure apparatus.

14. The optical system of claim 1 wherein the optical system is an optical system of a microlithographic projection exposure apparatus.

15. A microlithographic projection exposure process wherein an object plane of a projection objective is illuminated using an illumination system and wherein the object plane is imaged into an image plane of the projection objective using the projection objective;

wherein at least two different illumination settings are set using the illumination system; and

wherein between said illumination settings a polarization-influencing optical element which is made from optically active material with an optical crystal axis and which is of a thickness profile varying in the direction of said optical crystal axis is rotated about an axis of rotation, wherein said axis of rotation is arranged at an angle of 90°±5° relative to the optical system axis.