TaSiN thin-film pattern transfer optimization for 200 mm SCALPEL and extreme ultraviolet lithography masks

Abstract

Optimized etch processes for the pattern transfer of TaSiN-based SCALPEL and extreme ultraviolet lithography masks have been developed. For controllability, the etch rate is very commensurate with the pattern transfer of thin films, about 140 Å/min. Furthermore, selectivity to Cr at the process of record conditions (30 W radio frequency, 375 W inductively coupled plasma, 8 mT) is greater than 50:1, a necessity for pattern transfer on membrane-based masks. Critical dimension bias is on the order of 10 nm. For the fabrication of SCALPEL masks, supporting descum and Cr etch processes were also developed and are described later. Typical intramembrane uniformity of a 12.1 mm by 1.1 mm membrane processed through the entire pattern transfer sequence was found to be 8 nm, three sigma, which is quite favorable when compared with the starting resist uniformity (7 nm, three sigma). Similarly, using a test vehicle spanning 528 membranes, the intermembrane three sigma standard deviation was found to be 9 nm (starting resist uniformity of 8 nm, three sigma).