FABRICATION AND ANALYSIS OF EXTREME-ULTRAVIOLET REFLECTION MASKS WITHPATTERNED W C ABSORBER BILAYERS/

We report on a novel procedure developed for the fabrication of reflec tion masks for extreme ultraviolet lithography. The procedure involves the deposition and patterning of an absorber bilayer (40 nm W and 25 nm C) on Mo/Si multilayer blanks. The C layer is used to protect the u nderlying Mo/Si multilayer structure during processing and repair. The pattern is written with an e-beam pattern generator into EPR resist a nd is transferred into the absorber bilayer with three consecutive rf etching processes. We have investigated the effect of the full mask ma king procedure on the multilayer reflectivity using 13 nm radiation. T he procedure causes some oxidation of the top Si layer of the multilay er, an effect which is confirmed by XPS measurements. However, the met hod does not affect the multilayer reflectivity to within narrow toler ances. The profiles of patterns in the absorber layer are inspected wi th a SEM, showing patterns with a feature size of 250 nm and side wall slope angles of 80 degrees. An indication is found that cleaning of t he substrate with ion etching prior to the fabrication of the mask bla nks reduces the defect density. (C) 1997 American Vacuum Society.