Inorganic Resists for EUV Lithography

In Extreme UltraViolet Lithography (EUVL), exposure of a chemical resist to 13.5 nm light provides a means to create nanopatterns for the semiconductor industry. In EUVL, a silicon wafer is spin-coated with a thin, uniform layer of a light sensitive photoresist. Exposure to the light in specific areas on the wafer initiates reactions that change the photoresist’s solubility, enabling pattern development by washing with a suitable solvent. Although EUV resists in industrial use are made from organic polymers, they are not very sensitive to EUV irradiation. Inorganic compounds, such as metal oxide nanoparticles, have attracted recent interest as EUV resists, in part because of the higher EUV absorption of transition metals compared to the carbon, oxygen and hydrogen present in polymer-based resists. We are developing inorganic EUV resists based on highly EUV-absorbing transition metals and ligands. Because EUV irradiation generates secondary electrons that initiate the chemistry, we are studying our resist candidates by modelling the process with electron exposure. Our EUV resist work is carried out in collaboration with Prof. Howard Fairbrother at Johns Hopkins University.