Characterization of Directed Self Assembly Materials Using Soft X-Rays

The semiconductor industry continues to push the limits of photolithography with each subsequent generation of microchips. Block copolymer directed self assembly has been evaluated previously as a pitch reduction mechanism. It currently is being considered for applications of pattern rectification on extreme ultraviolet (EUV) lithography patterns. This would allow lower doses and higher throughput for EUV lithography. Questions remain about how the morphology and self assembly of the block copolymers result in the performance for pattern rectification. Additionally the push toward high numerical aperture EUV will result in patterns too small to rectify with PS-PMMA and necessitate the development of new block copolymers with a higher chi. Measurements are needed to characterize the new high chi block copolymers and to determine the chi. We will report on studies using a soft X-ray scattering method called resonant critical dimension small angle scattering (res-CDSAXS) to characterize the 3D morphology of block copolymers after directed self assembly. We will also discuss measurements using resonant soft X-ray reflectivity (RSoXR) to study the interfacial width and natural periodic spacing of block copolymer lamella. We will report these measurements on PS-PMMA and on newer high chi block copolymers. We will use the results of the 3D morphology and the interfacial width to provide general guidance on the design of new block copolymers.