Defect reduction and defect stability in IMEC's 14nm half-pitch chemo-epitaxy DSA flow

Directed Self-Assembly (DSA) of Block Co-Polymers (BCP) has become an intense field of study as a potential patterning solution for future generation devices. The most critical challenges that need to be understood and controlled include pattern placement accuracy, achieving low defectivity in DSA patterns and how to make chip designs DSA-friendly. The DSA program at imec includes efforts on these three major topics. Specifically, in this paper the progress in DSA defectivity within the imec program will be discussed. In previous work, defectivity levels of ~560 defects/cm2 were reported and the root causes for these defects were identified, which included particle sources, material interactions and pre-pattern imperfections. The specific efforts that have been undertaken to reduce defectivity in the line/space chemoepitaxy DSA flow that is used for the imec defectivity studies are discussed. Specifically, control of neutral layer material and improved filtration during the block co-polymer manufacturing have enabled a significant reduction in the defect performance. In parallel, efforts have been ongoing to enhance the defect inspection capabilities and allow a high capture rate of the small defects. It is demonstrated that transfer of the polystyrene patterns into the underlying substrate is critical for detecting the DSA-relevant defect modes including microbridges and small dislocations. Such pattern transfer enhances the inspection sensitivity by ~10x. Further improvement through process optimization allows for substantial defectivity reduction.