Extreme ultraviolet (EUV) lithography is considered as the leading patterning technology beyond the ArF-based optical
lithography, addressing the need for transistor densification to meet Moore's Law. Theoretically, EUV lithography at
13.5nm wavelength meets the resolution requirements for 1xnm technology nodes. However, there are several major
challenges in the development of EUV lithography for mass production of advanced CMOS devices. These include the
development of high power EUV light sources, EUV optics, EUV masks, EUV resists, overlay accuracy, and metrology
and inspection capabilities. In particular, it is necessary to ensure that effective defect control schemes will be made
available to reduce the EUV lithography defectivity to acceptable levels.
This paper presents a study on the wafer defectivity and characterization of patterned EUV resists, with the objective of
providing a quantitative comparison between the defectivity of different resist materials and different stacks. Patterned
wafers were printed using the ASML® EUV full-field Alpha-Demo Tool (ADT 0.25 NA) at imec. The EUV resist
patterns were 32nm line/spaces. Several advanced resist types were screened experimentally. The different resist types
and stacks were inspected using a DUV laser based brightfield inspection tool, followed by a SEM defect review and CD
metrology measurements. The patterns were characterized in terms of defect types and defect density.
We identified the major defect types and discuss factors that affect the defectivity level and pattern quality, such as resist
type, exposure dose and focus. Defect scattering analysis of DUV polarized light at different polarizations was
performed, to indicate on the inspection performance trends for a variety of defect types and sizes of the different resists
and stacks. The scattering analysis shows that higher defect scattering is induced using polarized light.