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Directed self-assembly (DSA) of block copolymer (BCP) thin films has been extensively researched as an alternative lithographic technology to enhance the resolution beyond the limitation of current lithography techniques.[1] One of the most critical factors need to be addressed for DSA process to be accepted at high volume manufacturing (HVM) is defect density of DSA pattern.[2] The defects of thermodynamically driven DSA process, such as the dislocation defects in LiNe flow, are known as kinetically trapped metastable structures.[3] Therefore, a key to eliminate those defects is to find out the effective kinetic pathway of assembly that enables BCP to reach to defect-free structure more easily. In addition to defect annihilation, easy pathway will also allow faster assembly, consequently reducing the cost of ownership of DSA process. The obvious approach for faster assembly in DSA process is to increase annealing temperature. In this study, we address the impact of annealing temperature on DSA process. First, increasing annealing temperature makes the free surface of a PS-b-PMMA film more PMMA preferential. Because of altered boundary condition at the top surface, more careful optimization of backfilling brush was required to maintain preferred orientation of BCP films. Second, the dimension of BCP is also affected by annealing temperature. Temperature dependency of BCP dimension was quantitatively investigated by CD-SEM and DSA-APPS Offline CD Measurement Software (Figure 1a). Based on the measured values, the dimension of chemical pattern is accordingly modified to achieve aligned DSA pattern (Figure 1b). We anticipate our finding from this study can be generally applied for other BCP systems.
[1] Ruiz, Ricardo, Huiman Kang, François A. Detcheverry, Elizabeth Dobisz, Dan S. Kercher, Thomas R. Albrecht, Juan J. de Pablo, and Paul F. Nealey. "Density multiplication and improved lithography by directed block copolymer assembly." Science 321, no. 5891 (2008): 936-939.
[2] Gronheid, Roel, Paulina Rincon Delgadillo, Hari Pathangi, Dieter Van den Heuvel, Doni Parnell, Boon Teik Chan, Yu-Tsung Lee et al. "Defect reduction and defect stability in IMEC's 14nm half-pitch chemo-epitaxy DSA flow." In SPIE Advanced Lithography, pp. 904905-904905. International Society for Optics and Photonics, 2014.
[3] Hur, Su-Mi, Vikram Thapar, Abelardo Ramírez-Hernández, Gurdaman Khaira, Tamar Segal-Peretz, Paulina A. Rincon-Delgadillo, Weihua Li, Marcus Müller, Paul F. Nealey, and Juan J. de Pablo. "Molecular pathways for defect annihilation in directed self-assembly." Proceedings of the National Academy of Sciences 112, no. 46 (2015): 14144-14149.
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