Mueller matrix optical scatterometry of Si fins patterned using directed self-assembly block copolymer line arrays

Directed self-assembly (DSA) based block copolymer (BCP) lithography shows promise as a cost-effective manufacturing technique for advanced sub-20 nm patterning. Characterization of types of defects and their levels in the sub-20 nm DSA patterns is a challenge for the current state-of-the-art metrology. Scatterometry has the capability of measuring important feature dimensions of DSA structures quickly and non-destructively at multiple steps in the process. This work is a report on the use of Mueller matrix spectroscopic ellipsometry (MMSE) based measurements of 28 nm pitch Si fins fabricated from DSA line patterns consisting of polystyrene-block-polymethylmethacrylate (PS-b-PMMA) fabricated using a chemical epitaxy process. A regression-based (inverse-problem) scatterometry approach was used to calculate the CD, line shapes, and thickness of the developed Si fin patterns. Sensitivity of MMSE to defectivity and line edge roughness (LER) in Si fin samples is discussed. At DSA dimensions the characterization of LER is crucial due to increase in the ratio between LER and target line width. HR-XRD and SEM imaging is also conducted as a comparative metric for scatterometry. This paper emphasizes the effectiveness of MMSE based scatterometry as a technique for optical characterization of Si fins fabricated with DSA lithography.