Topical Seminar Wednesday 12 December 2001 at 11.30
Venue: Alexanderzaal

Multilayer mirrors for EUV lithography: theoretical analysis

Igor V. Kozhevnikov

Lebedev Physical Institute, Leninsky prospect 53, Moscow 119991, Russia

As the application of multilayer reflecting optics in Extreme UV lithography progresses, more complex optical designs are being considered to further enhance the resolution and other imaging properties. By consequence, the multilayer system, being the essential part of the EUV imaging optics, is to meet these complex designs. Fortunately a number of free multilayer parameters exist, namely the materials of the multilayer, their composition and individual layer thicknesses, and the layer periodicity. Several design algorithms have been developed and are applied to different EUV multilayer designs in order to address the following problems:
- Maximum possible reflectance at 13.5 nm wavelength.
- The effect of protecting capping layers on the maximum reflectance.
- Multilayer designs with minimum field amplitude on a mirror surface.
- EUV multilayers with constant reflectivity in a wide angular range.
- EUV multilayers with constant phase of the reflected wave.