Block copolymer line roughness and annealing kinetics as a function of chain stiffness

Abstract

Block copolymers (BCPs) can phase separate to form periodic structures with small spacings that can be used to form a template. This template can then be used to pattern higher densities of features onto a substrate, thus extending optical lithography. Thin films of BCPs can have their features guided via chemoepitaxy by employing underlayers with a patterned chemical preference towards one of the blocks. Line edge roughness (LER) is defined as the spatial variation of the interface between the two blocks and this can be transferred to the features patterned by the BCP template. Electrical components with high LER in their features are known to have performance issues. Here, a molecular dynamics simulation was employed to model BCP chains in a thin film state. The BCP chains have an angle potential acting on them described by the two parameters kθ and θeq. Stiffness was varied by changing either the chain's resistance to bending (kθ) or how rod-like the chain is (θeq). It was found that while LER is unaffected by varying either parameter, line width roughness (variation in the width of a lamellae) increased with an increase in either parameter, though by an insignificant amount. Kinetic thin film simulations showed that increasing kθ increases the timescale for molecular diffusion while increasing θeq. potentially decreases the energetic barrier between a defect and defect-free state.