Extreme ultraviolet (EUV) photolithography has seen substantial interest from the semiconductor industry as a tool to create sub-10 nm features, which are necessary to improve device performance. However, EUV lithography will require new photoresist materials that absorb this light efficiently, maintain structural integrity under high-energy exposure, and are sufficiently thin to avoid pattern collapse. Many photoresists have been explored to meet this need, including polymer films with metal additives, and hafnia-based nanoparticle thin films. However, these resists tend to be limited to low viscosity resist formulations or use deposition methods, like spin coating, that struggle to form conformal coatings. One advanced manufacturing strategy for creating these resists involves using molecular layer deposition (MLD) to synthesize hybrid inorganic-organic films directly on the surface of interest.
MLD is a vapor-phase layer-by-layer thin film deposition process that can create films with subnanometer thickness and compositional control. While MLD has been used to make aluminum, hafnium, and tin-based EUV photoresists, films based on other elements may be beneficial for improving film stability in air and EUV-absorptivity.
In this work, we studied the stability and mechanical properties of organic-inorganic hybrid thin films deposited by MLD, for use in EUV photolithography applications. Using our previously published high-throughput multi-chamber MLD system, we synthesized and screened 18 different film chemistries using combinations of three inorganic elements—zinc, aluminum, and tin—and six organic precursors. These films were evaluated for stability in air, developer compatibility, and etchant resistance, both before and after UV exposure. Mechanical robustness was assessed using atomic force microscopy and nanoindentation. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to elucidate degradation pathways and confirm structural integrity. Selected high-performing materials were patterned using an electron beam source. Our findings reveal that specific combinations of organic and inorganic components yield films with significantly improved mechanical properties and stability in potential developers.
