Projection objective and method for its manufacture

A method, comprising:

• providing first and second mirror supports that are at least substantially identical;
• using light having a wavelength between 1 nm and 30 nm to measure an optical property of a first optical system comprising a first mirror, the first mirror comprising the first support and first reflective coating on the first support;
• changing a surface of the second mirror support based on the measured optical property of the first optical system;
• after producing the surface deformation in the second mirror support, applying a reflective coating on the second mirror support to provide a second mirror;
• and
• replacing the first mirror contained in the first optical system with the second mirror to provide an extreme ultraviolet (EUV) projection objective.

A method, comprising:

• a) providing a master mirror support;
• b) providing a slave mirror support which is an at least substantially identical copy of the master mirror support;
• c) applying a reflective coating on the master mirror support, thereby obtaining a master mirror;
• d) assembling a plurality of optical elements and the master mirror, thereby obtaining a preliminary optical system;
• e) measuring an optical property of the preliminary optical system;
• f) defining a surface deformation to be produced on the slave mirror support, thereby taking into account results obtained in the measuring step e);
• g) producing the surface deformation defined in step f) on the slave mirror support;
• h) applying a reflective coating on the slave mirror support reprocessed in step g), thereby obtaining a slave mirror;
• i) replacing the master mirror contained in the preliminary optical system by the slave mirror, thereby obtaining the optical system;
• wherein the optical system is a projection objective of a microlithographic projection exposure apparatus or an illumination system of a microlithographic projection exposure apparatus.