Design and analysis of a high-NA projection optical system for 0.35-μm deep-UV lithography

To meet the exacting demands of sub-half micron lithography, rigorous analysis must be a part of the entire optical design process. Several new modeling techniques have been developed to aid in determining the lithographic performance of an optical design. An aerial image modeling program has been implemented for the examination of CD variation and isolated/grouped line bias. Additional models have been developed to examine lens heating effects, stray light, and ghost images. A tolerancing technique has been established which provides maximum manufacturability while allowing minimal performance degradation. This design, analysis, and tolerancing process has yielded the first 31 mm field, 0.53 NA, 248 nm lithographic objective capable of producing 0.35 micrometers features in a manufacturing environment. The objective, as built, has a maximum astigmatism of 0.20 micrometers and a total focal plane deviation of 0.17 micrometers . A 1.3 micrometers common focus corridor in 1.0 micrometers thick APEX-E has been demonstrated for 0.35 micrometers features over the entire field. A grouped/isolated CD bias of 9 nm has been measured. This paper presents the design and analysis procedures along with the experimental results for this objective.