(708g) Symmetric Addition of Homopolymer on Ler/Lwr in Lamellae-Forming Directed Self-Assembled Block Copolymers

Block copolymers (BCPs) are an attractive material to the microelectronics industry due to their ability to microphase separate into morphologies (lamellae, cylinders, spheres, etc) with feature-to-feature spacings (pitch) ranging from 5 -100nm. As the industry tackles the challenges of continuing Moore’s Law, BCPs offer an alternative route to more expensive pathways such as Extreme Ultra-Violet Light lithography (EUVL). BCPs microphase separate when the enthalpic penalty between the two blocks of the BCP interacting is greater than the entropic penalty for them not mixing. This enthalpic penalty is directly related to the interaction parameter (χ) between the two blocks. By phase separating thin film BCPs (e.g. cylindrical or lamellae formers) the material can be used as a mask for transferring a pattern into a substrate. Directed self-assembly (DSA) is the process by which the BCP morphology’s direction is oriented and controlled. One method of accomplishing this is via chemoepitaxy which uses pre-patterns (pinning stripes) in the underlayer to preferentially place one block in a particular position along the substrate. The number of full pitch features that can form between any two pinning stripes is known as the density multiplication. The fact that the density multiplication is can be higher than 1x (one pinning stripe for every other lamellae) is one of the most attractive qualities of DSA of BCPs. This means that pre-patterns can be made at a lithographically cheaper cost than the patterns that are ultimately formed by the BCP.

Addition of homopolymer is known to increase the achievable pitch of BCP materials by segregating the homopolymer chains to the middle of the BCP lamellae domains. This blending is attractive because it lowers the critical need for very specific BCP molecular weights to reach a desired pitch. However, it’s not clear how increasing amounts of homopolymer affects the quality of the lamellae (e.g. line edge roughness, line width roughness, through-film shape, etc.). Roughness in the BCP’s features can lead to roughness in the transferred pattern in the substrate. It is known that roughness in the features composing a transistor can lead to performance issues. Here, we use coarse grained molecular dynamics simulations to probe the effect that symmetric homopolymer addition at different loadings has on the line edge- and line width roughness (LER/LWR) of lamellae forming BCPs on chemoepitaxial patterned underlayers. LER and LWR were measured while varying the width of the pinning stripes and the chemical composition of the region between pinning stripes in the underlayer.