Publications

We have measured the acid generation efficiency with EUV exposure of a PAG in different polymer matrixes representing the main classes of resist polymers as well as some previously described fluoropolymers for lithographic applications. The polymer matrix was found to have a significant effect on the acid generation efficiency of the PAG studied. A linear relationship exists between the absorbance of the resist and the acid generation efficiency. A second inverse relationship exists between Dill C and aromatic content of the resist polymer. It was shown that polymer sensitization is important for acid generation with EUV exposure and the Dill C parameter can be increased by up to five times with highly absorbing non-aromatic polymers, such as non-aromatic fluoropolymers, over an ESCAP polymer. The increase in the Dill C value will lead to an up to five fold increase in resist sensitivity. It is our expectation that these insights into the nature of polymer matrix effects on acid generation could lead to increased sensitivity for EUV resists.

The authors have developed an atomic-force-microscopy-based technique to measure intrinsic material roughness after base development. This method involves performing an interrupted development of the resist film and measuring the resulting film roughness after a certain fixed film loss. Employing this technique, the authors previously established that the photoacid generator (PAG) is a major material contributor of film roughness and that PAG segregation in the resist is likely responsible for nanoscale dissolution inhomogeneities. The additional roughness imparted on a test polymer by incorporation of a series of iodonium, sulfonium, diazo, and imido PAGs was measured. The roughness was then correlated to the inhibition properties of the various PAGs. This was accomplished both through a NMR technique that measures interaction of the PAG with the polymer and by evaluating the dissolution inhibition properties of the PAG through a percolation model. Several PAGs that result in significantly lower material roughness and thus the potential for significantly reduced linewidth roughness in resist imaging have been identified.