Ionic Interaction-Driven Polymer Blends for Achieving Small Feature Sizes

Direct self-assembly (DSA) using polymers with strong segregation strength has emerged as a promising solution to meet the demand for smaller critical dimensions at a lower cost, where achieving small feature sizes is crucial for enhancing the resolution and density of patterns in advanced semiconductor devices. Unlike traditional self-assembly driven by strong Flory-Huggins interactions or high values of segregation strength, χN, systems with ionic interactions can self-assemble into ordered structures in the weak segregation regime (WSL) at low values of χN. Therefore, with ionic interactions can form lamellar or cylindrical structures with shorter chains, enabling smaller feature sizes. Simulations using self-consistent mean field theory have been conducted, focusing on two key parameters: h, the free energy from ionic pair formation, and Nχ, the degree of segregation. In this presentation, we will discuss experimental measurements on blends of end-functionalized PS/PDMS telechelic polymers. Via small angle X-ray scattering (SAXS), we show that homo-telechelic PS/PDMS systems in the strong segregation limit revealed macrophase separation or disordered structures, aligning with the simulation results. This highlights a new feature of these systems, where a balance exists between segregation strength and ionic interactions. To test our findings, additional SAXS experiments were conducted on PS/PDMS blends in the WSL to determine how the ionic pair strength affects block copolymer self-assembly and achieve smaller feature sizes.