Employing a detailed compositional analysis to develop a low defect Mo/Si deposition tool and process for EUVL mask blanks

Extreme ultraviolet lithography (EUVL) is the leading lithography technology to fabricate critical feature sizes of 32 nm and smaller. For EUVL a Mo/Si multilayer-based reflective optical system is used and the development of suitable, defect-free mask blanks is the greatest challenge facing the commercialization of EUVL. In this paper we describe how a recently formed, state-of-the-art compositional analysis capability at the Mask Development Center at SEMATECH-North was utilized to identify the composition of defects in our process. This compositional information, coupled with tool and procedural upgrades based on best engineering practices and judgement, led to a decrease in the typical multilayer-coating-added defect density on 6 in. square quartz substrates by more than an order-of-magnitude, from ∼0.5 defects/cm2 to ∼0.028 defects/cm2 for particles ⩾80 nm in size (PSL equivalent). We have also obtained a “champion” mask blank with an added defect density of only ∼0.020 defects/cm2 for particles ⩾70 nm in size.