Dissolution characteristics of resist polymers studied by quartz crystal microbalance transmission-line analysis and pKa acidity analysis

The development process is very important in determining the resist resolution of lithography. Polymer dissolution during development was studied based on resonance frequency and impedance measured by the quartz crystal microbalance (QCM) method. A transmission-line analysis of QCM data was then carried out. The dissolution characteristics were also evaluated from the standpoint of molecular structures and polymer acidity measured by potentiometric titration. Fluoropolymers showed dissolution characteristics which reflect large fluorine effects in addition to acidity effects. The fluorine effects retarded the dissolution rates and formed a swelling layer. Poly(methacrylate)s had a complicated swelling behavior during development owing to the hydrophobic components in the polymers. The fluorine and hydrophobic effects rather than polymer acidity play the dominant role in forming the swelling layer during development.