3D TEM Tomography of Templated Bilayer Films of Block Copolymers
Kevin W. Gotrik, Thomas F. Lam, Adam F. Hannon, Wubin Bai, Jonathan P. Winterstein, Alfredo Alexander-Katz, James A. Liddle, Caroline A. Ross
Transmission electron microscope (TEM) tomography was used to visualize the morphology and 3D connectivity of a lithographically-templated, self-assembled bilayer film of cylinder-forming 45.5 kg/mol polystyrene-block-polydimethylsiloxane. The structure, formed after a 5 minute solvothermal anneal, was imaged with a resolution of ≅3 nm in 3D, enabling a comparison between measurement and self-consistent mean-field theory (SCFT) calculations. In addition to the general agreement between modeled and measured dimensions, the tomography revealed connections between the orthogonal layers of cylinders at their crossing point, a key model prediction. Validation of the SCFT model, even under solvothermal annealing conditions, suggests that it can be used to predict the detailed nanoscale structure of features created by directed self-assembly (DSA) with confidence, which is essential in developing nanomanufacturing processes based on DSA.