Thermal modulation during solvent annealing of PS-PDMS block copolymer

Abstract

The self-assembly of block copolymers (BCP) has been a promising area of research for nanolithography applications in microelectronics because of their ability to produce nano-scale level periodic structures with long-range order. Ideal BCPs for generating these nano-scale patterns fall within the strong segregation limit (SSL) and have a high interaction parameter to drive BCP phase transitions. BCP morphologies can vary from equilibrium structures such as spheres, cylinders, and gyroid, to metastable structures such as hexagonal perforated lamellar (HPL). A variety of processing techniques including solvent vapor annealing (SVA) have been developed in order to facilitate the phase transitions of BCPs from disordered to ordered states. SVA parameters which can affect the final film morphology include the swelling thickness of the film and solvent removal rate. Thermal modulation of the substrate was used to explore the effects of rapid solvent evaporation during the annealing process on the morphologies of the PS₁₆-b-PDMS₃₇ system. Additional cycles of solvent update and film reswelling were introduced into the annealing procedure to induce greater long-range ordering of film morphologies. Although a range of morphologies were explored, there was special focus on developing a procedure for mono-layer HPL structures for nanolithography applications.