Broad band DUV, VUV long-working distance catadioptric imaging system
AssigneeKLA-Tencor Technologies Corporation
InventorsDavid R. Shafer, Yung-Ho Chuang
Life of this patent
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Abstract
A high performance objective having very small central obscuration, an external pupil for apertureing and Fourier filtering, loose manufacturing tolerances, large numerical aperture, long working distance, and a large field of view is presented. The objective is preferably telecentric. The design is ideally suited for both broad-band bright-field and laser dark field imaging and inspection at wavelengths in the UV to VUV spectral range.
Claims38
A method of imaging an object, comprising:
- collecting light from said object with a focussing lens group;
- correcting chromatic aberration by use of a catadioptric group;
- and
- passing said light through a field lens group located between said focussing lens group and said catadioptric group;
- wherein said catadioptric group comprises a plurality of Mangin reflective elements and said light collecting occurs at a numerical aperture of in excess of 0.8.
A catadioptric optical system comprising:
- a focusing lens group at a high numerical aperture end of said system;
- a catadioptric group for at least partially correcting chromatic aberration, said catadioptric group comprising a plurality of Mangin reflective elements;
- and
- a field lens group located along an optical path between said focusing lens group and said catadioptric group.
A catadioptric optical system having a working distance between optical components and a specimen, comprising:
- a catadioptric group comprising a plurality of Mangin elements and having a relatively high degree of chromatic correction;
- and
- image forming optics producing an image of a surface being examined;
- wherein said working distance is at least 2 mm, and further wherein said catadioptric optical system exhibits a numerical aperture in excess of 0.8.
An apparatus for photolithographically imaging a semiconductor wafer, comprising:
- a focusing lens group at a high numerical aperture end of said apparatus;
- a catadioptric group for at least partially correcting chromatic aberration;
- and
- a field lens group located along an optical path between said focusing lens group and said catadioptric group;
- wherein said catadioptric group comprises a plurality of Mangin elements and said apparatus is configured to have a numerical aperture in excess of 0.8.
Dependencies are inferred from the claim text.