Macrocycle Network-Aided Nanopatterning of Inorganic Resists on Silicon

Inorganic resists have emerged as promising candidates in semiconductor industries to realize sub-10 nm node technology. However, controlling vertical shrinkage of resist films during the pattern development process, particularly for ultralow thin film applications, is among the highly pressing limitations of inorganic resists along with pattern roughness and poor resist shelf-life characteristics. Tin-based clusters and small molecules have been recently introduced as resist materials. They possess a high absorption coefficient and fast solubility transitions under irradiation exposure. As we investigated, n-butylstannoic acid (BTA) showed ∼38% vertical shrinkage when its film was exposed with deep ultraviolet photons (DUV, ∼254 nm) and could pattern features of ∼120 nm. We hypothesized and experimentally validated an approach that provided control on shrinkage issues, along with improving its patterning potential to sub-15 nm regime. In our approach, BTA was embedded into a polyhydroxy organic host matrix composed of noria (water-wheel-like macrocycle) derivatives. The rigid molecular cage structure and photo-inert nature of noria (N-Me) were utilized as the host matrix that apprehended the inorganic resist material within its intermolecular space. Ultrathin films (∼20 nm) were coated on silicon, and various nanofeatures including 10 nm lines, meshlike grids with 10 nm width, complex patterns, and so forth were patterned using electron beam and helium ion beam lithography. Most importantly, we were able to drastically reduce the vertical shrinkage to ∼13% with respect to initial thickness, which substantiates the potential of our hypothesis. We also noticed good shelf-life (6 months), good etch resistance, and low line edge roughness (LER)/line width roughness (LWR) for the developed resist composition.