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 32nm 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 6in. square quartz substrates by more than an order-of-magnitude, from ~0.5defects/cm^2 to ~0.028defects/cm^2 for particles >=80nm in size (PSL equivalent). We have also obtained a ''champion'' mask blank with an added defect density of only ~0.020defects/cm^2 for particles >=70nm in size.