Modeling Lithographically Induced Self-Assembly with Leaky Dielectric Films

IRG 2: L.F. Pease III and W.B. Russel

The lithographically induced self-assembly (LISA) process is initiated by positioning a template parallel to a flat silicon wafer coated with a thin polymeric film, leaving a thin gap filled with air or another polymer, and then raising the temperature above the glass transition/melting temperature of the film. Electric fields exert a force on free or polarization-induced charge at the polymer-air interface, placing the film in tension. The resulting static equilibrium is unstable to disturbances with sufficiently long wavelengths for the electrostatic force to overcome surface tension. Flow ensues, generating a pattern of cone-shaped spikes that develop into pillars with spacings reflecting the characteristic length of the instability. Leaky dielectric films (solid lines), which incorporate free charge, result in smaller spacings than perfect dielectric films (dashed lines), which do not. Data [Schäffer et al., Europhys. Lett., 53 (2001) 518] for brominated polystyrene (x), which may have free charge, agree quantitatively with the leaky dielectric theory, while data for polystyrene (+), without free charge, behaves as a perfect dielectric.

Related publication:
L. F. Pease III and W.B. Russel, “Electrostatically Induced Submicron Patterning of Thin Perfect and Leaky Dielectric Films: A Generalized Linear Stability Analysis”, J. Chem. Phys. 118, 3790 (2003).