Saddle-point construction in the design of lithographic objectives, part 2: application

Optical designers often insert or split lenses in existing de- signs. Here, we apply in the design of objectives for deep and extreme UV lithography an alternative method for adding new components that consists of constructing saddle points in the optical merit function land- scape and obtaining new local minima from them. The design examples show that this remarkably simple method can be easily integrated with traditional design techniques. The new method has significantly im- proved our design productivity in all cases in which we have applied it so far. High-quality designs of lithographic objectives are obtained with this method. © 2008 Society of Photo-Optical Instrumentation