Catadioptric projection objective

A projection exposure apparatus for microlithography, comprising:

• an illumination system configured to provide at least one illumination mode, and
• a catadioptric projection objective for microlithography and configured to image an object field in an object plane onto an image field in an image plane, comprising:
• an entrance pupil having a pupil radius,
• a first partial objective having a first optical axis and configured to image the object field onto a first real intermediate image,
• a second partial objective having a second optical axis and configured to image the first intermediate image onto a second real intermediate image, and
• a third partial objective having a third optical axis and configured to image the second intermediate image onto the image field,
• wherein the second partial objective has exactly one concave mirror and at least one lens,
• wherein the projection objective has a first folding mirror configured to deflect the radiation from the object plane toward the concave mirror and a second folding mirror configured to deflect the radiation from the concave mirror toward the image plane,
• wherein the projection objective forms exactly two real intermediate images,
• wherein the projection objective has a numerical aperture of greater than 1.0 in the image plane,
• wherein a minimum distance between an optically utilized region of the concave mirror and an optically utilized region of a surface, which faces the concave mirror, of a lens adjacent to the concave mirror is greater than 20 mm,
• wherein the illumination system is further configured to illuminate the entrance pupil of the projection objective with at least one illumination pole in the illumination mode,
• wherein the illumination pole represents a continuous region within the intensity distribution of the entrance pupil, in which the intensity does not fall below 10% of a maximum intensity,
• wherein, for all illumination poles of the illumination mode, a maximum extent of the illumination pole in the y direction is less than or equal to 8% of the pupil radius of the entrance pupil,
• wherein the y direction runs parallel to a straight line that is perpendicular to the first optical axis and lies within a plane of symmetry, and
• wherein the plane of symmetry is spanned by the first optical axis, the second optical axis and the third optical axis.

A method for operating a projection exposure apparatus for microlithography, comprising:

• providing at least one illumination mode with an illumination system, and
• imaging an object field in an object plane onto an image field in an image plane with a catadioptric projection objective which comprises:
• an entrance pupil having a pupil radius,
• a first partial objective having a first optical axis and imaging the object field onto a first real intermediate image,
• a second partial objective having a second optical axis and imaging the first intermediate image onto a second real intermediate image, wherein the second partial objective has exactly one concave mirror and at least one lens,
• a third partial objective having a third optical axis and imaging the second intermediate image onto the image field, and
• a first folding mirror deflecting the radiation from the object plane toward the concave mirror and a second folding mirror for deflecting the radiation from the concave mirror toward the image plane,
• wherein the projection objective forms exactly two real intermediate images,
• wherein the projection objective has a numerical aperture of greater than 1.0 in the image plane,
• wherein a minimum distance between an optically utilized region of the concave mirror and an optically utilized region of a surface, which faces the concave mirror, of a lens adjacent to the concave mirror is greater than 20 mm,
• wherein the illumination system, in accordance with the illumination mode, illuminates the entrance pupil of the projection objective with a differing number of illumination poles and with illumination poles of differing form,
• wherein each illumination pole represents a continuous region within the intensity distribution of the entrance pupil, in which the intensity does not fall below 10% of a maximum intensity,
• wherein a maximum extent of the illumination pole in the y direction is less than or equal to 8% of the pupil radius of the entrance pupil,
• wherein the y direction runs parallel to a straight line that is perpendicular to the first optical axis and lies within a plane of symmetry, and
• wherein the plane of symmetry is spanned by the first optical axis, the second optical axis and the third optical axis.

A method for operating a projection exposure apparatus for microlithography, comprising

• providing at least one illumination mode with an illumination system,
• imaging an object field in an object plane onto an image field in an image plane with a catadioptric projection objective which comprises:
• an entrance pupil having a pupil radius,
• a first partial objective having a first optical axis and imaging the object field onto a first real intermediate image,
• a second partial objective having a second optical axis and imaging the first intermediate image onto a second real intermediate image and having exactly one concave mirror and at least one lens, which is adjacent to the concave mirror,
• a third partial objective having a third optical axis and imaging the second intermediate image onto the image field,
• a first folding mirror deflecting the radiation from the object plane toward the concave mirror and a second folding mirror deflecting the radiation from the concave mirror toward the image plane,
• wherein the projection objective forms exactly two real intermediate images,
• wherein the projection objective has a numerical aperture of greater than 1.0 in the image plane,
• wherein a minimum distance between an optically utilized region of the concave mirror and an optically utilized region of a surface, which faces the concave mirror, of a lens adjacent to the concave mirror is greater than 20 mm,
• wherein the illumination system, in accordance with the illumination mode, illuminates the entrance pupil of the projection objective with a differing number of illumination poles and with illumination poles of differing form,
• wherein each illumination pole represents a continuous region within the intensity distribution of the entrance pupil, in which the intensity does not fall below 10% of a maximum intensity, and
• providing an illumination mode only when, on the surface, facing the concave mirror, of the lens adjacent to the concave mirror, a maximum surface power density is less than 0.6 W/cm2 while a total power of illumination light in the object plane is greater than 1.5 W.