Projection objective for microlithography
View Patent ↗A projection objective for microlithography for imaging a pattern arranged in the object plane of the projection objective into the image plane of the projection objective has at least one polarization splitter device that is operated only once in transmission or reflection. By using this device, polarization-dependent differences in the intensity and response of the light passing through the objective, which lead to a worsening of the imaging quality of the projection objective, can largely be avoided.
1. A projection objective for microlithography for imaging a pattern arranged in an object plane of the projection objective into an image plane of the projection objective, comprising:
between the object plane and the image plane, a catadioptric first objective part comprising a concave mirror and a beam deflection device and, behind the beam deflection device, a dioptic second objective part;
wherein the beam deflection device of the catadioptric first objective part comprises a first mirror surface for deflecting the radiation coming from the object plane to the concave mirror and a second mirror surface for deflecting the radiation reflected from the concave mirror in the direction of the second objective part, wherein at least one of the first mirror surface and the second mirror surface is a polarization splitter device which is operated only once in reflection between the object plane and the image plane; and
wherein the polarization splitter device is designed to discard a direction of polarization of light impinging on the polarization splitter device such that substantially only one direction of polarization contributes to the formation of an image in the image plane.
2. The projection objective according to claim 1 , wherein at least one delay element is fitted in the beam path downstream of the polarization splitter device, said delay element being formed such that the linear polarization produced by the polarization splitter device is substantially converted into circular polarization before the light exits from the projection objective.
3. The projection objective according to claim 1 , wherein the polarization splitter device is a polarization-selective dielectric multilayer system.
4. A projection objective for microlithography for imaging a pattern arranged in an object plane of the projection objective into an image plane of the projection objective, comprising:
between the object plane and the image plane, a catadioptric first objective part with a concave mirror and a beam deflection device and, behind the beam deflection device, a dioptric second objective part;
wherein the beam deflection device comprises a first mirror surface for deflecting the radiation coming from the object plane to the concave mirror and a second mirror surface for deflecting the radiation reflected from the concave mirror in the direction of the second objective part, wherein at least one of the first mirror surface and the second mirror surface is a polarization splitter device which is operated only once in reflection between the object plane and the image plane.
5. The projection objective according to claim 4 , wherein the first mirror surface is the polarization splitter device.
6. The projection objective according to claim 4 , wherein the second mirror surface is the polarization splitter device.