Abstract
Thin films formed by the condensation of metal oxo–hydroxo clusters offer a promising approach to ultrahigh-resolution patterning including next-generation photolithography using extreme ultraviolet (EUV) radiation and electron-beam lithography. In this work, we elucidate the thermal and radiative mechanisms that drive the chemical transformations in these materials and therefore control the patterning performance. Beginning from aqueous hafnium clusters, peroxide and sulfate additions serve to modify the clusters and, upon spin coating to form a thin film, provide the chemical contrast necessary to create resist. The coordination and functionality of peroxide and sulfate in hafnium-based metal oxo–hydroxo clusters were monitored at various stages of the patterning process which provided insight into the chemical and structural evolution of the material. Peroxide serves as the radiation sensitive species while sulfate enhances solubility and controls the concentration of hydroxide in the films. Peroxide and hydroxide species decompose via radiative and thermal energy, respectively, to form hafnium oxide; controlling these processes is central to the function of the resist.