Exploration of alternative resist materials for EUV lithography

Abstract A ladder-type silsesquioxane (SQ)-based material (containing organic functional groups) which utilizes direct photo-crosslinking as its main reaction mechanism for patterning, was developed and investigated for application in extreme ultraviolet (EUV) lithography. This negative-tone patterning material is soluble in the industry standard aqueous alkali developer 2.38 wt% tetramethylammonium hydroxide (TMAH). This work specifically reports on the utilization of a hydrogen-based photosensitive component i.e. “Sensitivity Enhancer” or SE to improve the SQ-based material’s EUV sensitivity. Fourier transform infrared spectroscopy results have shown that the introduction of components such as SE in the SQ-based material can promote the formation of Si–H compounds that upon EUV exposure will aid in the photo-crosslinking reactions, and consequently lead to improved EUV sensitivity. Furthermore, it was understood that the sensitivity enhancing effect of SE on the SQ material can be effectively taken advantaged of at concentrations greater than 10%. This was moreover substantiated by the EUV patterning results, where at 20% SE concentration in the SQ-based patterning material, a EUV sensitivity improvement of roughly 10% (compared to SQ material at no SE) was successfully obtained.