Polarized Soft X-ray Scattering to Interrogate Molecular Orientation in Block Copolymers

Block copolymers (BCPs) are attractive materials for nanopatterning applications at length scales between 5-50 nm. Patterning at future lithographic nodes will require BCPs with periodicities below 10 nm length scales, where the properties near the interface become increasingly important. However, direct experimental characterization of properties such as the extent of chain orientation near the interface remains challenging. Polarized soft X-ray scattering (PRSoXS) is one potential route for interrogating these properties. Polarized soft x-rays are sensitive to the molecular orientation of specific chemical bonds, and there has recently been significant progress towards quantitative interpretation of PRSoXS patterns. Measurements have been conducted on a series of BCPs with variations in chemistry and molecular weight and characterized with PRSoXS at both the carbon and oxygen edge. The results of these measurements show polarization induced anisotropy in the scattering pattern, which are indications of molecular orientation in the system. The relationships between the molecular orientation and predictions of BCP interface width will be discussed.