Determining Structure of Lamellar A-b-(B-r-C) Copolymers with Soft X-ray Reflectivity

Nanostructured polymer thin films have been studied for a variety of applications including electronic transistors, membranes for separations, and bit-patterned media. We have devised a model block copolymer system to systematically tune the interaction parameter, χ, through use of modular A-b-(B-r-C) copolymers. The nanostructure can be tuned by changing the chemical identities of blocks B and C, as well as the molar ratio of component B to C, φ. This modular polymer architecture allows for precise tuning of the block copolymer periodicity, L₀, for a prescribed value of segregation strength, χN. Through resonant soft X-ray reflectivity (RSoXR), we have determined the effect of φ on the interface width and lamellar spacing on thin films of lamellar block copolymers oriented parallel to the substrate. It is hypothesized that the interface width is directly related to the line edge roughness of patterned block copolymers, an important property for applications in directed self-assembly. We will compare the results from reflectivity to measurements of line-edge and width roughness of perpendicular oriented polymer thin films via image analysis of SEM micrographs. Our results provide insights into how copolymer structure affects block copolymer self-assembly and roughness in polymer thin films.