Image quality and pattern transfer in directed self assembly with block-selective atomic layer deposition

Self-assembled block copolymer patterns may render more robust masks for plasma etch transfer through block-selective infiltration with metal oxides, affording opportunities for improved high contrast, high fidelity pattern transfer for sub-15 nm lithography in wafer-scale processes. However, block selective infiltration alters the self-assembled block copolymer latent image by changing feature size, duty cycle, and sidewall profile. The authors systematically investigate the effects of aluminum oxide infiltration of 27 and 41 nm pitch line/space patterns formed using polystyrene-b-poly(methyl methacrylate) block copolymers and evaluate the process compatibility with directed self assembly. The degree of image distortion depends on the amount of infiltrated material, with smaller amounts resulting in complete mask hardening and larger amounts shifting and collapsing pattern features. An attractive feature of the resulting oxide mask is the relatively smooth line edge roughness of the final transferred features into Si with a 3 sigma = 2.9 nm line edge roughness. (C) 2012 American Vacuum Society. [http://dx.doi.org/10.1116/1.4758773]