차세대 극자외선 노광 기술에서의 Flare Effect에 관한 연구

Abstract

Extreme ultraviolet lithography (EUVL) using a light of 13.5nm wavelength is a leading candidate for 22nm lines and space (L/S) half pitch node and beyond. Its implementation into high-volume manufacturing has been investigated with alpha demo tool (ADT) at IMEC. Unlike current 193nm ArF lithography, transmissive optical components cannot be available in EUVL imaging systems. Only reflective optical components and masks are needed in EUVL, because a light of 13.5nm wavelength is not transmitted, but absorbed by most of materials. One of the critical issues in extreme ultraviolet lithography (EUVL) is flare, which is an integrated light scattering from surface roughness in the EUVL optical system. Flare degrades the control of critical dimension (CD) uniformity across the exposure field. Also, it generates larger CD sensitivity as line and space (L/S) half pitch size decreases. Therefore, we discussed the calculation of accurate fine-grid flare maps to compensate for flare variation. The influence of three-dimensional (3D) mask topography on flare was investigated with different absorber thicknesses, off-axis illumination angles, and azimuthal angles. Also, some types of dummy patterns were found to be effective in controlling the flare variation within a L/S patterned target and the average flare of a L/S patterned target. Our studies has definitely made progress in an effective flare variation compensation using a rule-based correction for sub-22nm L/S half pitch node and beyond.