Extreme ultraviolet lithography mask patterning and printability studies with a Ta-based absorber

Extreme ultraviolet (EUV) lithography masks were fabricated using a stack o f TaSi or TaSiN (absorber), SiON (repair buffer), and Cr (conductive etch s top) on a Mo/Si multilayer mirror deposited on a Si wafer. High-resolution structures were exposed using a commercial i-line resist, and the pattern w as transferred using both electron cyclotron resonance and reactive ion etc hing with halogen-based gases. Process temperatures to fabricate these reti cles were always maintained below 150 degrees C. EUV properties after patte rning were measured using a synchrotron source reflectometer. Completed mas ks exhibited a negligible shift in the peak wavelength and less than 2% los s in reflectivity due to processing. Qualified masks were exposed with a 10 x EUV exposure system. The exposures were made in 80-nm-thick DUV resist an d with numerical apertures (NA) of 0.08, 0.088, and 0.1. Resolution down to 70 nm equal lines and spaces was achieved at a NA of 0.1. Line edge roughn ess in the resist features was 5.5 nm (3 sigma, one side), and the depth of focus for +/-10% CD control was +/-1 mu m for 100 nm equal lines and space s. (C) 1999 American Vacuum Society. [S0734-211X(99)07706-9].