Status of fabrication of square format masks for extreme ultraviolet lithography (EUVL) at the MCoC

Fabricating masks for extreme ultraviolet lithography is challenging. The high absorption of most materials at 13.4 nm and the small critical dimension (45 nm) at the target insertion node force many new features, including reflective mask design, new film choices, and stringent defect specifications. Fabrication of these masks requires the formation and patterning of both a repair buffer layer and an EUV absorber layer on top of a molybdenum/silicon multi-layer substrate. IBM and Photronics have been engaged in developing mask processing technology for x-ray, electron beam projection and extreme ultraviolet lithographies at the Next Generation Lithography Mask Center of Competency (NGL-MCoC) within IBM's mask facility at Essex Junction, Vermont. This paper describes recent results of mask fabrication on 6 x 6 x (1)/(4) inch EUVL substrates (quartz with molybdenum silicon multi-layers) at the MCoC. Masks fabricated with high and low-stress chromium and externally deposited chromium absorber films are compared. In particular, etch characteristics, image size, image placement, fine edge roughness, and defect levels are presented and compared. Understanding the influence of the absorber film characteristics on these parameters will enable us to optimize the effectiveness of a given absorber film or to select acceptable alternatives.