Application of quantitative structure property relationship to the design of high refractive index 193i resist

A robust quantitative structure property relationship (QSPR) model with five parameters has been developed from 126 organic compounds for the prediction of refractive index at 589 nm. The model and the knowledge of the refractive index dispersion were used in the rational design of new materials for 193-nm immersion lithography. The significance of this model is that the structural descriptors can be readily calculated and the factors that significantly affect refractive index can be easily identified and used to guide the selection of candidates. Using this model, rapid screening of large structure databases is possible in order to find candidates. As an example of this approach, the synthesis of the copolymer of a trithiocyclane-methacrylate derivative, identified by the model, with 2-methyl adamantyl methacrylate is described. The measured refractive index of the copolymer at 589 nm agrees well with the value predicted by the model. The new polymer showed a 9.4% increase in refractive index at 193 nm compared with the standard ArF resist.