Peak and Integrated reflectivity, wavelength and gamma optimization of Mo/Si, and Mo/Be multilayer, multielement optics for extreme ultraviolet lithography

Reported is the optimization of the fabrication of Mo/Si multilayer systems produced by e-beam evaporation and ion-beam smoothening. The impact of a n umber of coating parameters is verified such as variation of the mirror's c enter wavelength and the metal fraction of the bilayer (Gamma ratio), resul ting in reflectivities up to 68.6% at normal incidence. Parallel to this ex perimental work, a numerical optimization based on experimentally determine d multilayer properties is carried out on the throughput of multimirror lit hographic systems for the 11-15 nm wavelength region using Mo/Si and Mo/Be coatings. The center wavelength, Gamma ratio and layer stack have been opti mized. The calculations show an optimum throughput for a 10-mirror Mo/Si sy stem at 14.4 nm, assuming a light source with a wavelength independent spec trum. (C) 1999 American Vacuum Society. [S0734-211X(99)12106-1].