With the development of the lithography technologies to create smaller features with higher NA, lower k1 values and shorter wavelengths, homogeneity specifications for fused silica blanks continue to tighten³. Fused silica and calcium fluoride are the only material for the DUV lithography objective. One of the difficult problems for the lithography is how to deal with the capability of the optical material. The inhomogeneity will influence the quality of lithography objective and is an important specification. In order to obtain relative homogeneity specifications for each fused silica blanks of the overall lithography objective, we can iterate the lenses of the lithography objective in turn, one piece lens at a time, which the iterated one has the same spherical gradient index, we can obtain the RMS wavefront errors of all fields after every iterativeness. When all iterativeness is implemented, we can find the difference between design and results of iterativeness. The degradation of the RMS wavefront errors is larger; the lens iterated is more sensitive for index. According to the RMS wavefront errors of iterative results, we can make a conclusion that homogeneity specification for fused silica blanks of the lithography lens is extraordinarily different, not all lens need the same homogeneity specifications. It is known, higher homogeneity, more expensive. So we can choose the different homogeneity grade fused silica blanks.

Date Published: 12 October 2010
PDF: 6 pages
Proc. SPIE 7656, 5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 76564F (12 October 2010); doi: 10.1117/12.866846

Published in SPIE Proceedings Vol. 7656:
5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment
Yudong Zhang; Jose M. Sasian; Libin Xiang; Sandy To, Editor(s)