Mechanistic Study of HafSO_<i>x</i> Extreme Ultraviolet Inorganic Resists

Abstract

Inorganic resists are promising for nanomanufacturing because of their potential for high-resolution and low line-edge roughness patterning and exceptional sensitivity to extreme ultraviolet (EUV) radiation. Hafnium oxide peroxide hydroxide sulfate (HafSOx) is a model EUV inorganic photoresist, wherein the EUV absorption coefficients for hafnium and O are much higher than for conventional polymer resists. Absorption of EUV radiation leads to electron emission that results in the HafSOx solubility change. We used desorption-based techniques to elucidate thermal- and radiation-induced processes that contribute to the HafSOx solubility switch. We found that low kinetic energy electrons render HafSOx insoluble and result in the desorption of molecular O2. Electron-stimulated desorption and postexposure Raman spectroscopy indicate similar kinetics for peroxide loss in HafSOx. Temperature-programmed desorption studies found that peroxide ligand desorption is best characterized as first order, with a broad distribution of thermal desorption energies. Finally, a pair distribution function analysis of X-ray scattering data of HafSOx solutions and powders provides an atomic-level model of local structure within the film that is consistent with other characterization data of solutions and deposited films.