Extreme ultraviolet mask fabrication with high inspection contrast TaSiNx absorber stack

Abstract

Extreme ultraviolet lithography (EUVL) is a leading candidate for next generation lithography with the potential for extendibility beyond the 45 nm node. The three-layer absorber stack for EUVL reticles consists of an absorber, repair buffer and etch stop layers, while a two-layer absorber stack eliminates the etch stop layer. Improving inspection contrast is critically important to finding defects. In previous work, using TaSiN as the EUV absorber, the inspection contrast was less than 10%, which did not allow for effective defect detection to occur. However, other TaSiN properties such as thin film stress control and critical dimension etch bias were clearly superior to the Cr absorber. An improved process using a Ta-based absorber stack that maintains the beneficial characteristics of the film, on SEMI Standard P1-92 6025 format substrates, is discussed.