Scattering of EUV optics: substrate, coating, and degradation effects

Scattering resulting from interface imperfections crucially affects the throughput and image contrast of EUV optics. Since both the substrate finish and the intrinsic thin film roughness influence the scattering, thorough investigations are needed to separate the different effects and to identify the most promising starting points for further optimizations. Mo/Si multilayer coatings deposited onto different substrates are investigated by utilizing an instrument for EUV reflectance and scattering measurements at 13.5 nm recently developed at the Fraunhofer IOF. The influences of the substrate finish and the deposition process onto the scattering are separated. Furthermore, the instrument allowed the EUV-induced degradation of Mo/Si mirrors to be investigated at the wavelength of application. In particular the impact of top-layer oxidation and roughening on the scattering properties is discussed.

[1]  Regina Soufli,et al.  Sub-diffraction-limited multilayer coatings for the 0.3 numerical aperture micro-exposure tool for extreme ultraviolet lithography. , 2007, Applied optics.

[2]  Sasa Bajt,et al.  High-temperature stability multilayers for extreme-ultraviolet condenser optics. , 2005, Applied optics.

[3]  D. Gaines,et al.  Nonspecular x-ray scattering in a multilayer-coated imaging system , 1998 .

[4]  Kenneth A. Goldberg,et al.  EUV scattering and flare of 10X projection cameras , 1999, Advanced Lithography.

[5]  N. Kaiser,et al.  EUV multilayer optics , 2006 .

[6]  M. Chandhok,et al.  Effects of flare in extreme ultraviolet lithography: Learning from the engineering test standa) , 2004 .

[7]  J. P. Rahn,et al.  Relationship of the total integrated scattering from multilayer-coated optics to angle of incidence, polarization, correlation length, and roughness cross-correlation properties. , 1983, Applied optics.

[8]  David L. Windt,et al.  IMD—software for modeling the optical properties of multilayer films , 1998 .

[9]  Raj Korde,et al.  Present status of radiometric quality silicon photodiodes , 2003 .

[10]  Angela Duparre,et al.  Scatter analysis of optical components from 193 nm to 13.5 nm , 2005, SPIE Optics + Photonics.

[11]  Sergey Yulin,et al.  Multilayer Coatings for EUV/Soft X-ray Mirrors , 2003 .

[12]  Larissa Juschkin,et al.  Status of EUV-lamp development and demonstration of applications , 2004, SPIE Advanced Lithography.

[13]  Andreas Tünnermann,et al.  EUV reflectance and scattering of Mo/Si multilayers on differently polished substrates. , 2007, Optics express.

[14]  Donald W. Sweeney,et al.  Fabrication and testing of optics for EUV projection lithography , 1998, Advanced Lithography.

[15]  Torsten Feigl,et al.  EUV multilayer mirrors with enhanced stability , 2006, SPIE Optics + Photonics.