Block copolymers (BCP) are considered one of the leading materials for next generation nanolithography due to their ability to self-assemble into sub-20 nm features. Directed self-assembly (DSA) of BCP, through chemically or topographically substrate pre-patterning, enables control over the self-assembly process, resulting in uniform BCP morphologies over macroscopic length scale. However, it’s recently been shown that the potential of BCP in patterning applications depends critically on the three-dimensional (3D) structure of the assembled domains. Moreover, since BCP assembly is inherently a 3D process, it is necessary to characterize the 3D morphology in order to fully understand the development of 3D structures and the relationship between the substrate’s guiding patterns and the assembled BCP films in DSA films.<br/>Here we used scanning transmission electron microscopy (STEM) tomography and coarse-grained simulations to probe the 3D structure of DSA films on pre-patterned templates. We quantified the domain structure and its fluctuations as a function of depth, with respect to the position, chemistry, topography, and geometry of the underlying template. The 3D characterizations revealed non-vertical, 3D morphologies that were hidden underneath the surface and were not probed by conventional surface imaging. In addition, the tomographic characterization and simulations of BCP defects shed light on possible origins of common DSA defects. Positional fluctuation characterization, conducted on the tomographic data, showed variation in roughness with depth and with lamella location in the assembled unit cell. The knowledge obtained on the 3D assembly of BCP films in this study will enable better design of materials and processes for patterning applications.

Three-dimensional assembly of block copolymers on pre-patterned templates

254th National Meeting (2017)

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