Progress towards the development of a commercial tool and process for EUVL mask blanks

Abstract

Extreme ultraviolet lithography (EUVL) is the leading next generation lithography (NGL) technology to succeed optical lithography at the 32 nm nodes and beyond. The technology uses a multilayer-based reflective optical system and the development of suitable, defect-free mask blanks is one of the two greatest challenges facing the commercialization of EUVL. In this paper we describe recent progress towards the development of a commercial tool and process for the production of EUVL mask blanks. Using the resources at the recently formed Mask Blank Development Center at SEMATECH-North we have been able to decrease the mean multilayer-coating-added defect density by almost an order of magnitude, from ~0.5 defects/cm² to ~0.055 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 ~ 0.005 defects/cm². This advance was due primarily to a compositional analysis of the particles followed by tool and procedural upgrades based on best engineering practices and judgment. Another important specification for masks blanks is the coating uniformity and results showing good uniformity with the low defect density coating process are also presented.