New robust edge detection methodology for qualifying DSA characteristics by using CD SEM

Grapho-epitaxy based hole shrink process of Directed Self-assembly (DSA) is one of the candidates for less than 30 nm hole pattern fabrication. The guide patterns of grapho-epitaxy are made by using ArF immersion scanner under the condition of near resolution limit to the 193-nm exposure. Hence, guide patterns have measurable level of edge roughness and edge placement errors. Those errors cause serious size errors and placement errors of DSA hole patterns. RED (Robust Edge Detection) is a new measurement function of CD-SEM for qualifying guide pattern shapes and DSA pattern shapes simultaneously. We also propose GBM (Grid Based Metrology) for the measurement of DSA hole's absolute placement error. In this paper, we applied the two methods for qualifying about 20 nm-node's different polymer film thickness of DSA hole process. The DSA placement error from GBM result and relative DSA placement error obtained by RED are almost same as about 3nm (3sigma). This indicates both RED and GBM methods are correct to measure the DSA process error.