Reflecting Multilayer Coatings for EUV Projection Lithography

In the past 20 years, a very large effort has been devoted to the development of multilayer reflecting coatings for the x-ray and extreme ultraviolet (EUV) spectral regions. Out of this development arose the concept of EUV projection lithography, and multilayer coating represents the key technology which enable EUVPL. At the same time it presents technical challenges to be overcome for EUVPL to become a production tool.

These lie in the physics and chemistry of the multilayers, in the deposition technology and in the metrology of the final coatings. In this paper these topics are reviewed, and some interesting results obtained using the soft x-ray/EUV Calibration and Standards beamline at the Advanced Light Source are presented.