A hybrid polymeric material bearing a ferrocene-based pendant organometallic functionality: synthesis and applications in nanopatterning using EUV lithography

Largely because of their unique physical and chemical properties, the inclusion of ferrocene derivatives into polymer backbones has attracted great attention in materials research as these hybrid organometallic polymers find wide applications in various fields. Though chemically amplified photoresists (CARs) have become the workhorses for nanopatterning in semiconductor industries, due to several inherent problems CARs cannot be used for sub 20 nm technology and therefore non-chemically amplified resists (n-CARs) are gaining attention from the photoresists community, considering their potential in patterning sub 20 nm features with good line edge roughness/line width roughness (LER/LWR) and high resolution. Given that extreme ultraviolet lithography (EUVL) is approaching well towards the commercialization phase, the present work describes the development of novel solution processable EUV-sensitive hybrid organic–organometallic polymeric non-chemically amplified photoresist materials containing pendant ferrocene units and their applications in featuring 25 nm lines and complex nanopatterns using EUVL. This resist design is accomplished by copolymers that are prepared from monomers containing sulfonium groups which are sensitive to EUV irradiation. The copolymers were characterized by 1H NMR and IR spectroscopic techniques, gel permeation chromatography as well as thermal analyses. Whereas the photon-directed polarity change at the sulfonium center followed by scission of the polymer backbone nullified the requirement for chemical amplification, the inclusion of organometallic species in the polymer microstructure into the polymer network improved the thermal stability of the resultant hybrid system.