Influence of Additives on the Interfacial Width and Line Edge Roughness in Block Copolymer Lithography

The challenges of patterning next-generation integrated circuits have driven the semiconductor industry to look outside of traditional lithographic methods in order to continue cost-effective size scaling. The directed self-assembly (DSA) of block copolymers (BCPs) is a nanofabrication technique used to reduce the periodicity of patterns prepared by traditional optical methods. BCPs with large interaction parameters (χ_eff) provide access to smaller pitches and reduced interface widths. Larger χ_eff are also expected to be correlated with reduced line edge roughness (LER), a critical performance parameter in integrated circuits. One approach to increasing χ_eff is blending the BCP with a phase-selective additive, such as an ionic liquid (IL). The IL does not impact the etching rates of either phase, and this enables a direct interrogation of whether the change in the interface width driven by higher χ_eff translates into a lower LER. The effect of the IL on the layer thickness and the interface width of a BCP is examined, along with the corresponding changes in LER in a DSA-patterned sample. The results demonstrate that increased χ_eff through additive blending will not necessarily translate to a lower LER, clarifying an important design criterion for future material systems.